Citrix VDI Handbook and Best Practices

XenApp and XenDesktop 7.15

Long Term Service Release

Version 2.01

Citrix VDI Handbook - XenApp and XenDesktop 7.15 LTSR 
 
 
Table of Contents 
Section 1: Overview ................................................................................................................................................ 10 
Introduction .............................................................................................................................................................................................. 10 
Methodology ........................................................................................................................................................................................... 11 
Section 2: Assess ...................................................................................................................................................... 12 
Overview ..................................................................................................................................................................................................... 12 
Step 1: Define the Organization .................................................................................................................................................. 12 
Step 2: Define the User Groups .................................................................................................................................................... 13 
Step 4: Define the Applications .................................................................................................................................................... 21 
Step 5: Define the Project Team .................................................................................................................................................. 23 
Section 3: Design ..................................................................................................................................................... 32 
Overview ..................................................................................................................................................................................................... 32 
Layer 0: Conceptual Architecture ................................................................................................................................................ 32 
Layer 1: The User Layer ....................................................................................................................................................................... 37 
Layer 2: The Access Layer .................................................................................................................................................................. 45 
Layer 3: The Resource Layer ............................................................................................................................................................ 63 
Layer 4: The Control Layer ................................................................................................................................................................ 93 
Layer 5: The Hardware Layer ....................................................................................................................................................... 131 
Section 4: Monitor ................................................................................................................................................ 141 
Overview .................................................................................................................................................................................................. 141 
Process 1: Support ............................................................................................................................................................................. 141 
Process 2: Operations ...................................................................................................................................................................... 153 
Process 3: Monitoring ...................................................................................................................................................................... 165 
Acknowledgments ............................................................................................................................................... 179 
Authors ..................................................................................................................................................................................................... 179 
Subject Matter Experts .................................................................................................................................................................... 179 
Revision History ................................................................................................................................................................................... 180 
 
   

Citrix VDI Handbook - XenApp and XenDesktop 7.15 LTSR

Disclaimer

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this document, including, but not limited to, implied warranties of merchantability and fitness for any

particular purpose. This document may contain technical or other inaccuracies or typographical errors.

Citrix Systems, Inc. reserves the right to revise the information in this document at any time without notice.

This document and the software described in this document constitute confidential information of Citrix

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Agreement

About Citrix

Citrix (NASDAQ:CTXS) is leading the transition to software-defining the workplace, uniting virtualization,

mobility management, networking and SaaS solutions to enable new ways for businesses and people to

work better. Citrix solutions power business mobility through secure, mobile workspaces that provide

people with instant access to apps, desktops, data and communications on any device, over any network

and cloud. With annual revenue in 2015 of $3.28 billion, Citrix solutions are in use at more than 330,000

organizations and by over 100 million users globally. Learn more at www.citrix.com.

trademarks of Citrix Systems, Inc. and/or one of its subsidiaries, and may be registered in the U.S. and other

countries. Other product and company names mentioned herein may be trademarks of their respective

companies.

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Section 1: Overview

Introduction

In traditional business environments, workers suffer from productivity loss in many ways, including

downtime during PC refreshes, patches and updates, or simply when they are away from the office.

Application and desktop virtualization centralizes apps and desktops in the datacenter, rather than on local

devices. This allows IT to deliver apps and desktops to users on demand, to any device, anywhere.

Take the following response from a desktop virtualization user:

Unfortunately, organizations sometimes struggle to achieve this level of success. Why does one

organization succeed while another organization struggles?

If we compare the factors between success and failure between desktop virtualization and other

technology related projects, we see that there is little difference:

1. Lack of justification – Without a solid business reason, desktop virtualization is simply a new way to

deliver a desktop. A business justification gives the project team a goal to strive towards.

2. Lack of a methodology – Many people who try and struggle to deploy a desktop virtualization

solution do so because they jump right in without understanding or implementing the

appropriate prerequisites. A structured methodology provides the path for the project.

3. Lack of experience – For many who embark on a desktop virtualization project, there is a lack of

experience, which creates a lack of confidence in the design. Architects begin to second-guess

themselves and the project stalls.

Our hope is that this handbook can alleviate the anxiety associated with desktop virtualization by showing

how challenges can be resolved in a manner that is technically sound, but also feasible and effective for

organizations facing deadlines and other organizational challenges.

Citrix has successfully employed the methodology, experience and best practices shared within this

handbook across thousands of desktop virtualization projects.

Experience from the Field

As a remote employee for [company], I struggled every time I needed to access the company’s intranet,

which forced me to VPN into the network. I also kept data on my local device because trying to access

it over my broadband connection was too slow. Some coworkers did the same and lost data due to a

virus, thankfully I was luckier.

Depending on my mood (and the weather), changing devices and locations was a challenge as I had to

have my applications and data copied to many different endpoints. I know this was unsecure, but I

didn’t care because I was more concerned with flexibility.

Since moving to a virtual desktop, I’m able to use any device. I’m able to work from any location. And

best of all, I don’t have to worry about copying my data and applications onto all of my personal

devices.

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Methodology

The Citrix VDI Handbook follows the Citrix Consulting methodology. A proven methodology that has been

successfully employed across thousands of desktop virtualization projects. Each phase includes guidance

on the important questions to ask, what tools to use and tips to help you succeed. The Citrix Consulting

methodology consists of five phases:

Figure 1: Citrix Consulting Methodology

1. Define – Builds the business case for desktop virtualization by creating a high-level project roadmap,

prioritizing activities and estimating storage and hardware requirements.

2. Assess – Key business drivers are rated so that work effort can be prioritized accordingly. In addition,

the current environment is reviewed for potential problems and to identify use cases for the project.

This information will be used to set the direction of the Citrix deployment, upgrade, or expansion.

3. Design – Define architecture required to satisfy key business drivers and success criteria identified

during the assess phase. Topics such as environment scalability, redundancy and high availability are

addressed.

4. Deploy – During the deploy phase, the infrastructure is installed and configured as described in the

design phase. All components of the infrastructure should be thoroughly unit and regression tested

before users are provided with access to the environment.

5. Monitor – Define architectural and operational processes required to maintain the production

environment.

The Citrix Consulting methodology follows an iterative Assess > Design > Deploy process for each major

initiative of your project. In doing so, your organization is left with tangible improvements to the

environment at the end of each engagement. For example, high priority user groups can progress through

the assess, design and deploy phases earlier than other user groups

Note: The VDI Handbook provides content on the Assess, Design and Monitor phases of the Citrix Consulting

methodology.

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Section 2: Assess

Overview

Creating an app and desktop delivery solution begins with a proper assessment. Architects that fail to

properly assess the current environment find that they require the assess information later on, forcing

them to backtrack, which can potentially stall and put the project at risk.

By gathering all of the information from the outset, the architect will gain an appreciation for the current

environment and be able to work from the beginning on properly aligning business and user requirements

with the overall solution.

The assess phase is a four-step, simple to follow process:

Figure 2: Assess Process

Step 1: Define the Organization

The first step in your virtual desktop project should be to understand and prioritize the strategic

imperatives of the organization. This enables the project management team to define success criteria and

allows the design team to create a tailored and optimized architecture.

Requirements can be captured during meetings or by distributing questionnaires. Meetings are more time

consuming, but allow for follow-up questions to be asked and help to simplify the prioritization process. It

is important that this exercise be completed jointly by both business managers and IT decision makers

since both groups will have significantly different viewpoints. Take the following examples of what certain

organizations faced, which drove their selection of desktop virtualization.

These are just a few examples, but they demonstrate how organizations think about their priorities. Most

organization do not focus on technology, they focus on the needs of the user and of the organization.

These needs can be met with technical solutions but it is imperative the team understands the “Why” of

the project.

Define the

organization

Define the user

groups

Define the

applications

Define the

project team

Experience from the Field

Finance – A large financial institution had a base of operations in the city designated as the host city for

an upcoming G8 summit. As these types of meetings historically include riots, protests and other issues

that can disrupt business and the safety of their employees, the financial organization needed an

alternative allowing their users to work from the safety of their homes.

Agriculture – Due to thin margins, an agriculture organization wanted to save money by extending the

life of desktop PCs while still being able to run the latest applications.

Healthcare – A large healthcare organization was in need of a solution to simplify application updates

as the main application required updates on a weekly basis. Due to the distributed nature of the

endpoint devices, the organization was in need of a better application delivery solution.

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In addition to the three real-world examples, the following table identifies a few other priorities often

stated from many organizations:

Requester

Requirement

Business managers

Better IT agility and responsiveness – Flexible desktop solution that is capable of

accommodating periods of change such as rapid growth or downsizing. For example,

enabling the business to setup project offices or temporary points of sale very rapidly

without long delays, hardware acquisitions or IT notification periods.

Bring your own device – Empower employees to choose their own devices to improve

productivity, collaboration and mobility.

Collaboration – With an increase in both globalization and mobility, team members are

often dispersed across multiple physical locations. Powerful collaboration capabilities are

required to ensure high levels of productivity, efficiency and quality.

Work from anywhere – The business needs to support home workers in order to attract and

retain top talent, and / or travelling employees.

IT decision makers

Better desktop management – Simplify the management of desktop infrastructure. IT is not

as proactive as they would like and spend too much time “fighting fires”.

Increase security – Data theft or the loss of devices containing sensitive data is a big risk and

preventive measures are a top priority.

Extend desktop hardware lifecycle – Replacing workstations every three to five years in

order to keep up with the requirements of the operating system or the applications has

been very costly.

Reducing IT Management Scope – Improve IT efficiency by focusing on only the aspects

driving the business while offloading remaining functions to 3

parties via cloud or service

providers.

Improving user experience - Increasing performance or enabling features which would

otherwise not be possible with a geographically dispersed user population

Table 1: Sample Business Drivers

The prioritization process should be completed in collaboration with the project team, business managers

and IT managers so that all views are considered.

Step 2: Define the User Groups

Although there are multiple approaches towards defining user groups, it is often easiest to align user

groups with departments as most users within the same department or organizational unit consumes the

same set of applications.

User Segmentation

Depending on the size of the department, there might be a subset of users with unique requirements.

Each defined user group should be evaluated against the following criteria to determine if the

departmental user group needs to be further divided into more specialized user groups.

 Primary datacenter

– Each user will have a primary datacenter or cloud resource location

assigned that will be used to host their virtual desktop, data, and application servers. Identify

the datacenter that the user should be assigned to rather than the datacenter they are

currently using. Users will be grouped based on their primary datacenter so that a unique

design can be created for each one.

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 Personalization

– Personalization requirements are used to help determine the appropriate VDI

model for each user group. For example, if a user group requires complete personalization, a

personal desktop will be recommended as the optimal solution. There are three classifications

available:

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Personalization

Requirement

None

User cannot modify any user or application

settings, for example - kiosk.

Basic

User can modify user-level settings of desktops

and applications.

Complete

User can make any change, including installing

applications.

Table 2: Personalization Characteristics

 Security

– Security requirements are used to help determine the appropriate desktop and

policy (or policies) for each user group. For example, if a user group requires high security, a

hosted pooled desktop or a local VM desktop will be recommended as the optimal solution.

There are three classifications available:

Security Level

Description

Low

Users are allowed to transfer data in and out of the

virtualized environment.

Medium

All authentication and session traffic should be

secured; users should not be able to install or modify

their virtualized environment.

High

In addition to traffic encryption, no data should leave

the data center (such as through printing or

copy/paste); all user access to the environment

should be audited.

Table 3: Security Characteristics

 Mobility

– Mobility requirements are used to help determine the appropriate desktop model

for each user group. For example, if a user group faces intermittent network connectivity, then

any VDI model requiring an active network connection is not applicable. There are four

classifications available:

Mobility

Requirement

Local

Always uses the same device, connected to an

internal, high-speed and secured network.

Roaming Local

Connects from different locations on an internal,

high-speed, secured network.

Remote

Sometimes connects from external variable-speed,

unsecure networks.

Mobile

Often needs access when the network is

intermittent or unavailable.

Table 4: Mobility Characteristics

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 Desktop Loss Criticality

– Desktop loss criticality is used to determine the level of high

availability, load balancing and fault tolerance measures required. For example, if there is a

high risk to the business if the user’s resource is not available, the user should not be allocated

a local desktop because if that local desktop fails, the user will not be able to access their

resources. There are three classifications available:

Desktop loss

criticality

Requirement

Low

No major risk to products, projects or

revenue.

Medium

Potential risk to products, projects or

revenue.

High

Severe risk to products, projects or

revenue.

Table 5: Desktop loss criticality Characteristics

 Workload –Types and number of applications accessed by the user impacts overall density and

the appropriate VDI model. Users requiring high-quality graphics will either need to utilize a

local desktop implementation or a professional graphics desktop. There are three

classifications available:

User Type

Characteristics

Light

1-2 office productivity apps or kiosk.

Medium

2-10 office productivity apps with light

multimedia use.

Heavy

Intense multimedia, data processing or

application development.

Table 6: Workload Characteristics

Note: Performance thresholds are not identified based on processor, memory or disk utilization

because these characteristics will change dramatically following the application rationalization

and desktop optimization process. In addition, it is likely that the user’s management tools and

operating system will change during the migration process. Instead, workload is gauged based on

the number and type of applications the user runs.

Experience from the Field

Utility company – A large utility company collected data on every user in their organization. During

the user segmentation process, it was realized that the organization’s existing role definitions were

sufficiently well defined that all the users within a role shared the same requirements. This allowed a

significant amount of time to be saved by reviewing a select number of users per group.

Government – A government organization discovered that there was significant deviation between

user requirements within each role, particularly around security and desktop loss criticality. As such,

each user needed to be carefully reviewed to ensure that they were grouped appropriately.

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Assign VDI Models

As with physical desktops, it is not possible to meet every user requirement with a single type of VDI.

Different types of users need different types of resources. Some users may require simplicity and

standardization, while others may require high levels of performance and personalization.

Implementing a single VDI model across an entire organization will inevitably lead to user frustration

and reduced productivity.

Citrix offers a complete set of VDI technologies that have been combined into a single integrated

solution. Because each model has different strengths, it is important that the right model is chosen for

each user group within the organization.

The following list provides a brief explanation of each VDI model.

 Hosted Apps – The hosted apps model delivers only the application interface to the user. This

approach provides a seamless way for organizations to deliver a centrally managed and hosted

application into the user’s local PC. The Hosted Apps model is often utilized when organizations

must simplify management of a few line-of-business applications. Hosted apps includes a few

variants:

 Windows Apps – The Windows apps model utilizes a server-based Windows operating

system, resulting in a many users accessing a single VM model.

 VM Hosted Apps – The VM hosted apps model utilizes a desktop-based Windows

operating system, resulting in a single user accessing a single VM model. This model is

often used to overcome application compatibility challenges with a multi-user operating

system, like Windows 2008, Windows 2012 and Windows 2016.

 Linux Apps – The Linux apps model utilizes a server-based Linux operating system,

resulting in a many users accessing a single VM model.

 Browser Apps – The browser apps model utilizes a server-based Windows operating

system to deliver an app as a tab within the user’s local, preferred browser. This approach

provides a seamless way for organizations to overcome browser compatibility challenges

when users want to use their preferred browser (Internet Explorer, Microsoft Edge,

Google Chrome, Mozilla Firefox, etc.) but the web application is only compatible with a

specific browser.

 Shared Desktop – With the shared desktop model, multiple user desktops are hosted from a

single, server-based operating system (Windows 2008, 2012, 2016, Red Hat, SUSE, CentOS and

Ubuntu). The shared desktop model provides a low-cost, high-density solution; however,

applications must be compatible with a multi-user server based operating system. In addition,

because multiple users share a single operating system instance, users are restricted from

performing actions that negatively impact other users, for example installing applications,

changing system settings and restarting the operating system.

 Pooled Desktop – The pooled desktop model provides each user with a random, temporary

desktop operating system (Windows 7, Windows 8 and Windows 10). Because each user receives

their own instance of an operating system, overall hypervisor density is lower when compared to

the shared desktop model. However, pooled desktops remove the requirement that applications

must be multi-user aware and support server based operating systems.

 Personal Desktop – The personal desktop model provides each user with a statically assigned,

customizable, persistent desktop operating system (Windows 7, Windows 8, Windows 10, Red

Hat, SUSE, CentOS and Ubuntu). Because each user receives their own instance of an operating

system, overall hypervisor density is lower when compared to the shared desktop model.

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However, personal desktops remove the requirement that applications must be multi-user aware

and support server based operating systems.

 Pro Graphics Desktop – The pro graphics desktop model provides each user with a hardware-

based graphics processing unit (GPU) allowing for higher-definition graphical content.

 Local Streamed Desktop – The local streamed desktop model provides each user with a centrally

managed desktop, running on local PC hardware

 Local VM Desktop – The local VM desktop model provides each user with a centrally managed

desktop, running on local PC hardware capable of functioning with no network connectivity.

 Remote PC Access – The remote PC access desktop model provides a user with secure remote

access to their statically assigned, traditional PC. This is often the fastest and easiest VDI model to

deploy as it utilizes already deployed desktop PCs.

Each user group should be compared against the following table to determine which VDI model

best matches the overall user group requirements. In many environments, a single user might utilize

a desktop VDI model and an app VDI model simultaneously.

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Segmentation

Characteristic

Hosted Apps

Hosted

Shared

Desktop

Hosted

Pooled

Desktop

Hosted

Personal

Desktop

Hosted Pro

Graphics

Desktop

Local

Streamed

Desktop

Local

Desktop

Remote PC

Access

Workload

Light





Medium



Heavy





Mobility

Local



Roaming Local





Remote







Mobile







Personalization

None





Basic





Complete









Security

Low

Medium



High









Desktop Loss Criticality

Low

Medium





High





“”: Recommended, ““: Not Recommended, “º” Viable

Table 7: VDI Model Capability Comparison

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Don’t forget to follow these top recommendations from Citrix Consulting based on years of

experience:

Citrix Consulting Tips for Success

1. Start with Windows apps, shared and pooled desktops – As you can see in the VDI capability

table above, the Windows apps, hosted shared and pooled desktop models can be used in

the majority of situations. The local streamed and local VM desktop models should only be

used on an exception basis. By reducing the number of VDI models required, you will help to

reduce deployment time and simplify management.

2. Perfect match – It may not be possible to select a VDI model that is a perfect match for the

user group. For example, you can’t provide users with a desktop that is highly secure and

offers complete personalization at the same time. In these situations, select the VDI model

which is the closest match to the organization’s highest priorities for the user group.

3. Desktop loss criticality – There are only three VDI models that meet the needs of a high

desktop loss criticality user group (backup desktops available) – none of which allow for

complete personalization. If a high-desktop loss criticality user group also requires the ability

to personalize their desktop they could be provided with a pool of backup desktops (hosted

shared, pooled) in addition to their primary desktop. Although these desktops would not

include customizations made to their primary desktop, they would allow users to access core

applications such as mail, Internet and Microsoft Office.

4. Consider Operations & Maintenance – The ongoing support of each VDI model should be

factored in when deciding on a VDI model. For example, pooled desktops can be rebooted

to a known good state which often leads to reduced maintenance versus a personal desktop

where each desktop is unique.

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Step 4: Define the Applications

Once the users have been divided up in to groups the next step is to determine which applications they

require. This is a two-step process:

1. Application rationalization – Help to simplify the application assessment by removing redundant

applications from the inventory that were captured during the data capture.

2. Link apps to users – Use the results from the data capture process to map applications to user

groups.

Application Rationalization

The number of applications identified during the inventory is often surprising, even for organizations

that believe they have a high-level of control over applications. To help reduce complexity as well as

overall time required, it’s important to take the time to consolidate the list of applications.

The following guidelines will help ensure that your application list is consolidated appropriately:

 Multiple versions – Different versions of the same application may have been identified during

the inventory. There are various reasons for this, including an inconsistent patching or upgrade

process, decentralized application management, limited licenses and situations where users

require specific application versions for compatibility with other applications, macros and

document formats. Where possible, work with the application owners to reduce the number of

versions required. The leading practice is to standardize on a single version of each application,

typically the latest.

 Non-business applications – Applications that are not required by the business should be

removed from the application inventory to reduce resource requirements and to help simplify

the overall project. Non-business related applications are typically found in an application

inventory when users have been provided with the ability to install their own applications and

typically include games, communication clients, screen savers, peripheral software and media

players.

 Legacy applications – The inventory may identify legacy applications that have since been

retired or that are no longer required within the business. These applications may not have

been removed from the desktops because there is no established process to do so or because

there are always more high-priority activities to complete. These applications should be

consolidated during the rationalization stage of the application assessment.

 Management applications – The antivirus, application delivery, monitoring, inventory,

maintenance and backup applications will be completely re-designed across the organization

during the desktop virtualization project. These applications should also be consolidated

during this stage.

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Application Categorization

Each application included in the project should be categorized based on certain criteria, which will help

determine the most appropriate way to host and integrate the app. Each application can be installed

directly into the image, virtualized in an isolated container and streamed to the desktop (Microsoft

App-V), captured in a unique layer and attached to the virtual machine (Citrix App Layering) or installed

locally on the user’s endpoint device and seamlessly integrated into the user’s virtual desktop (Citrix

Local App Access). Due to the uniqueness of every application, many large-scale deployments

simultaneously utilize multiple approaches.

Each application should be categorized as follows:

 Common Apps - Every organization includes a suite of applications utilized by almost every

user, Microsoft Office for example. This suite of applications is often the most utilized

application in a desktop VDI model.

 Departmental Apps - A certain set of applications are only relevant for a unique business unit

or department. For example, an engineering department will often require software

development applications.

 User Apps - Often making up the largest grouping of apps are the apps used by very few

individual users. In a traditional PC implementation, these applications are installed by the user

as a temporary requirement or a personal requirement, often not directly impacting the

business.

 Management Apps – Many desktop deployments include a combination of antivirus,

monitoring, inventory, maintenance and backup applications. Many of these applications have

unique virtualization requirements and are often required across the entire organization.

Application Characterization

The following characteristics should be identified for each application so that the right application

delivery model can be selected during the design phase of the project:

 Complex – An application should be classified as complex or technically challenging if it is

difficult to set up, has extensive dependencies on other applications or requires a specialized

configuration, for example an Electronic Medical Records (EMR) application. Complex

applications need to be identified during the application assessment because they are not

generally appropriate for installation in a pooled/personal desktop model or delivery by

application streaming. Delivering complex applications as a hosted app often helps to reduce

the complexity of the base desktop image.

 Demanding – Collecting application resource requirements allows the virtualization

infrastructure to be sized and an appropriate application delivery model to be selected. For

example, demanding or resource intensive applications will not be delivered via a

Experience from the Field

Government: A government organization identified that there were 2,660 applications installed

across their desktop estate. Most of which were installed by users with local administrative rights. By

following the application rationalization recommendations above, it was possible to reduce the

number of applications required to 160.

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pooled/personal desktop model because there is limited control over how the resources are

shared between users. There are two classifications available in the user assessment worksheet:

Workload

Requirement

Resource

Intensive

Application requires 1GB+ of RAM or

averages 50%+ CPU utilization.

None

The application is not resource

intensive.

Table 8: Application Workload Characteristics

 Mobile – Some user groups may require the ability to work while mobile, sometimes when

offline. If so, it is important that the design can determine which applications will work without

a network connection and which ones will not. Applications that require backend infrastructure

such as web and database servers are not typically available offline.

 Peripherals – If applications require connectivity with peripheral devices, identify the interface

required so that it can be made available to the application when it is run from a virtual session.

 Restrictions – Application access may need to be restricted due to insufficient licenses /

resources and to protect sensitive data / tools. For example, applications with a limited number

of licenses should not be installed on a base image that is shared with unlicensed users. There

are three restricted access categories in the application assessment workbook:

Restricted Access

Requirement

There are no restrictions for the application and it

can be accessed by any user within the organization.

User group

The application may be installed on a multi-user

operating system but only a specific group of users

should be provided with an icon.

Virtual machine

Application should only be installed on a virtual

machine that is accessible by authorized users, often

because of licensing requirements.

Table 9: Restricted Access Characteristics

Step 5: Define the Project Team

Desktop virtualization is a fundamental change that requires close collaboration between various business

and technical teams in order to be successful. For example, the virtualization and desktop teams need to

work together to ensure that the virtual desktop image meets user needs while also being optimized for

the datacenter. Failure to build a cohesive project team that consists of the right roles and skillsets can

negatively impact performance, availability, user experience and supportability while also increasing costs

and risk.

The following tables identify the business and technical roles required during an enterprise virtual desktop

deployment. Although the list may seem quite large, many of these roles are only required for a short time

and multiple roles may be performed by a single person. The project manager and Citrix architect are

considered to be full time roles with other team members being brought in only when required. The

project manager role is key to ensuring that the right people are involved in the project at the right time.

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Business Roles

Role

Description

Example Responsibilities

Project sponsor

The project sponsor is a senior

company executive who

recognizes the benefits that

desktop virtualization will bring to

the business. The project sponsor

role is often performed by the

chief technology officer (CTO).

Pre-project

 Promote desktop virtualization within

business

 Identify members of the steering

committee

Secure funding

 Assess general costs associated with

solution

 Identify and prioritize key business drivers

Project manager

The project manager directs the

project team and is responsible for

ensuring that project objectives

are completed on time and within

budget.

All steps

 Define key project milestones

 Create and update project plan

 Track progress against plan

 Track expenditure against budget

 Maintain issue and risk register

 Manage scope changes

 Create weekly project reports

 Brief steering committee on progress

 Organize project workshops and meetings

 Ensure project teams are synchronized

 Ensure pre-requisites are in place

 Creates change control requests

Business

manager

Depending on company structure

and size, business managers

oversee planning and

performance at a department,

region or company level. A

business manager understands the

requirements necessary for their

employees to be successful.

Assess

 Assist with application consolidation

project

 Provide details on connectivity

requirements of user group, including

offline usage

 Provide details on risk tolerance of user

group

 Identify requirements for peripherals

Deploy

 Promote benefits of desktop virtualization

 Assist with coordinating the rollout

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Business

continuity

manager

The business continuity manager

ensures that an organization can

continue to function after a

disruptive event such as natural

disaster, crime or

human/computer error.

Assess

 Provide Citrix architect with detailed

understanding of the current business

continuity plan

Design

 Update business continuity plan to

incorporate the new Citrix infrastructure

Deploy

 Test business continuity plan

Test manager

The test manager is responsible for

ensuring that the test and user

acceptance environments match

the production environment as

closely as possible. The test

manager helps to reduce risk by

ensuring that changes are fully

tested before being implemented

in production.

Assess

 Provide Citrix architect with detailed

understanding of current testing

infrastructure and processes

Design

 Work with Citrix architect to design an

appropriate testing infrastructure and test

plan for new Citrix environment

Deploy

 Ensure that testing design is implemented

correctly and new Citrix infrastructure is

fully tested before rollout

Application

owners

An application owner is a subject

matter expert on specific

applications deployed within the

business. Application owners are

responsible for ensuring that

problems with the applications are

resolved and that

upgrades/updates are performed

without issue. Application owners

are also responsible for managing

support agreements with the

application vendors.

Assess

 Assist with application consolidation

project

 Identify application licensing limitations

 Provide details on security restrictions

 Provide details on application

dependencies

 Provide location of backend resources

Deploy

 Provide installation pre-requisites and

install guide

 Assist Citrix team with installing and testing

applications in VDI environment

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Service desk

manager

The service desk manager helps to

improve productivity and end-user

satisfaction by ensuring that

production issues are logged,

escalated and resolved in a timely

manner. The service desk manager

is also responsible for reporting on

common issues, call volumes and

service desk performance.

Assess

 Identify common issues with existing

environment

 Provide details on support tools currently

used

Design

 Assist Citrix architect with designing a

delegated administration model

 Participate in operations and support

design workshops

 Work with training manager to identify

training requirements

Deploy

 Monitor helpdesk calls for rollout related

issues

Training

manager

The training manager ensures that

support staff and end-users are

proficient with new areas of

technology. The training manager

also has responsibility for ensuring

that the training plan is up-to-date

and followed appropriately.

Assess

 Determine current skill set for support staff

and end users

Design

 Create training plan for support staff and

end users

Deploy

 Implement training plan for support staff

and end users

Communications

manager

The communication manager is

responsible for disseminating key

information throughout the

organization.

Design

 Work with project manager to create

communications plan

Deploy

 Relay benefits of desktop virtualization

 Inform users of key migration dates

 Ensure expectations are set accordingly

Table 10: Business Roles

Technical Roles

Role

Description

Example Responsibilities

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Citrix desktop

architect

The Citrix architect acts as the

design authority for all Citrix

products and liaises with other

architects to ensure that the Citrix

infrastructure is successfully

integrated into the organization.

Assess

 Work with project sponsor and key

stakeholders to identify and prioritize key

business drivers

 Oversee user segmentation and app.

assessment

 Map VDI models to user groups

 Perform capabilities assessment to

determine current state of readiness

 Identify areas of risk and provides remedial

actions

Design

 Create Citrix design that includes hardware

and storage estimates

 Coordinate with other architects to

integrate Citrix infrastructure into

organization

 Work with monitoring architect to ensure

that Citrix environment is monitored

appropriately

 Create operations and support design

 Create implementation and rollout design

 Create test plan

Deploy

 Ensure that the Citrix environment is

implemented in accordance with design

 Verify that implementation passes test plan

 Ensure that the Citrix design is

implemented correctly

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Active directory

architect

Design authority on Microsoft

Active Directory, including

Organizational Units (OU) and

Group Policy Objects (GPOs).

Assess

 Provide Citrix architect with detailed

understanding of current Active Directory

architecture

Design

 Work with the Citrix architect to design OU

structure, group policies, permissions,

service accounts, etc. for new Citrix

environment

 Update Active Directory infrastructure

design to reflect centralization of user data

and accounts

Deploy

 Ensure that Active Directory design is

implemented correctly

Virtualization

architect

Design authority on server and

desktop virtualization using Citrix

XenServer, Microsoft Hyper-V,

Nutanix Acropolis or VMware

vSphere.

Assess

 Provide Citrix architect with detailed

understanding of current virtualization

architecture

Design

 Work with Citrix architect to design

hardware, networking, storage, high

availability, etc. for server and desktop

virtualization

 Work with monitoring architect to ensure

that virtualization environment is

monitored appropriately

Deploy

 Ensure that the virtualization design is

implemented correctly

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Network

architect

Design authority on networking,

including routing, VLANs, DHCP,

DNS, VPN and firewalls.

Assess

 Provide Citrix architect with detailed

understanding of current networking

architecture

Design

 Work with Citrix architect to design physical

network, virtual networks, routing, firewalls,

quality of service, remote access, network

optimization, etc. for new Citrix

environment

 Work with monitoring architect to ensure

that network is monitored appropriately

Deploy

 Ensure that network design is implemented

correctly

Desktop

architect

Design authority on Microsoft

desktop operating systems,

including Windows XP, Windows 7

and Windows 8.

Assess

 Provide Citrix architect with detailed

understanding of current desktop

environment

Design

 Work with Citrix architect to design core

desktop virtual image, core applications,

desktop optimizations, etc. for new Citrix

environment

 Work with monitoring architect to ensure

that the virtual desktops are monitored

appropriately

Deploy

 Ensure that desktop design is implemented

correctly

Storage

architect

Design authority on storage

solutions, including direct-

attached storage, storage-

attached networks and network

attached storage.

Assess

 Provide Citrix architect with detailed

understanding of current shared storage

environment

Design

 Work with Citrix architect to design storage

architecture, tiers, sizing, connectivity, etc.

for new Citrix environment

 Work with monitoring architect to ensure

that storage is monitored appropriately

Deploy

 Ensure that storage design is implemented

correctly

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Backup

architect

Design authority on backup and

recovery, including virtual

machines, desktops, servers, user

data and databases.

Assess

 Provide Citrix architect with detailed

understanding of current backup

architecture and processes

Design

 Work with Citrix architect and disaster

recovery architect to design backup

architecture, process, schedule, retention,

etc. for new Citrix environment

Deploy

 Ensure that backup design is implemented

correctly

Application

packaging

architect

Design authority on packaging

applications for deployment via

the systems management team.

Assess

 Provide Citrix architect with detailed

understanding of current application

packaging process and status

Deploy

 Ensure that all required applications are

packaged according to design

Monitoring

architect

Design authority on monitoring,

including hardware, network,

servers, storage and security

appliances.

Assess

 Provide Citrix architect with detailed

understanding of current monitoring

architecture and processes

Design

 Work with Citrix architect to design

monitoring architecture, metrics, alerts, etc.

for new Citrix environment and supporting

infrastructure

Deploy

 Ensure that monitoring design is

implemented correctly

 Provide regular reports on capacity and

trends during rollout

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Systems

management

architect

Design authority on systems

management, including

server/desktop build process,

patching and automated

application installation.

Assess

 Provide Citrix architect with a detailed

understanding of the current systems

management processes

Design

 Works with Citrix architect to define

server/desktop build process, patching and

application delivery strategy for new Citrix

environment

Deploy

 Ensure that the systems management

design is implemented correctly

Security

architect

Design authority on security,

including desktops, servers,

networks and VPNs.

Assess

 Provide Citrix architect with detailed

understanding of current security policy

Design

 Work with Citrix architect to design security

standards for new Citrix environment,

including authentication, encryption, port

numbers, firewall rules, etc.

Deploy

 Ensure that security design is implemented

correctly

Table 11: Technical Roles

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Section 3: Design

Overview

Designing a desktop virtualization solution is simply a matter of following a proven process and aligning

technical decisions with organizational and user requirements. Without the standardized and proven

process, architects tend to randomly jump from topic to topic, which leads to confusion and mistakes. The

recommended approach focuses on working through five distinct layers:

Figure 3: Five-Layer Design Model

The top three layers are designed for each user group independently, which were identified during the

user segmentation section of the assess phase. These layers define the users’ resources and how users

access their resources. Upon completion of these three layers, the foundational layers (control and

hardware) are designed for the entire solution.

This process guides the design thinking in that decisions made higher up impact lower level design

decisions.

Layer 0: Conceptual Architecture

The conceptual architecture helps define the overarching strategies for the entire solution based on

business objectives and organizational structure.

Although an organization’s conceptual architecture will change over the coming years, it is worthwhile to

start the design phase by defining the long-term objectives around delivery models and the physical,

geographical distribution of solution.

Decision: Delivery Model

A XenDesktop and XenApp solution can take on many delivery forms. The organization’s business

objectives help select the right approach.

Even though the infrastructure remains the same for all delivery models, the local IT team’s

management scope changes.

User Layer User Layer User Layer User Layer

Access Layer Access Layer Access LayerAccess Layer

Resource Layer Resource Layer Resource LayerResource Layer

Control Layer

Host Layer Host Layer Host Layer

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 On Premises - All components hosted from the organization’s local data center. The on-

premises model requires the local IT team to manage every aspect of the solution.

Figure 4: On-Premises Architecture

 Public Cloud - All components hosted from a public cloud infrastructure using Infrastructure

as a Service (IaaS). The public cloud model eliminates hardware management from the local IT

team‘s management scope.

Host

Access Control ResourcesUsers

DirectorLicensesStudio

XenApp / XenDesktop

Controller

Database

StoreFront

NetScaler

On-Premises

Devices

User

Pooled Windows Desktops

Linux Apps

Windows Apps

Host

Access Control ResourcesUsers

DirectorLicensesStudio

XenApp / XenDesktop

Controller

Database

StoreFront

NetScaler

Devices

User

Pooled Windows Desktops

Linux Apps

Windows Apps

Cloud

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Figure 5: Public Cloud Architecture

 Hybrid Cloud - A single implementation executes from an on-premises data center as well as

the public cloud. Even though components of the solution are using different hosting

providers, the entire solution is a single solution using the same code and managed as a single

entity. The local IT team continues to manage all aspects of the solution except for the

hardware associated with the cloud-hosted resources.

Figure 6: Hybrid Cloud Architecture

 Citrix Cloud - The XenApp and XenDesktop Service offering from Citrix Cloud breaks a typical

deployment into multiple management domains. The access and control layer components

are hosted and managed in the Citrix cloud by Citrix while the resource layer components

continues to be managed by the local IT team either as an on-premises, public cloud or hybrid

cloud model. Citrix manages the hardware, sizing and updates to the access and control

components while the local IT team manages the resources. In addition, if the public cloud

hosts the resources, the local IT team does not have to manage the resource hardware. Citrix

Cloud continues to expand the number of offerings to help solve specific user cases. To learn

Host

Access Control ResourcesUsers

DirectorLicensesStudio

XenApp / XenDesktop

Controller

Database

StoreFront

NetScaler

On-Premises

Devices

User

Pooled Windows Desktops

Linux Apps

Windows Apps

On-Premises

Cloud

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more and understand the full array of offerings, please explore the workspace services within

the Citrix Cloud.

Figure 7: Citrix Cloud Architecture

Decision: Site Topology

A XenApp and XenDesktop site groups desktops and applications together to form a single

architectural and management entity. All persistent and dynamic data for the site, including site

configuration, desktop assignments, and session state, is stored in a site’s database.

A site can be contained within a single location, span across multiple locations or be a partial location.

Through rigorous testing, a single XenApp/XenDesktop site can support 40,000 or more concurrent

sessions.

Figure 8: Delivery Site Design Examples

Host

Access Control ResourcesUsers

DirectorLicensesStudio

XenApp / XenDesktop

Controller

Database

StoreFront

NetScaler

Devices

User

Pooled Windows Desktops

Linux Apps

Windows Apps

On-Premises

Cloud

Citrix Cloud Citrix Cloud

Cloud Connector

Data Center 4

Concurrent Users: 150

Applications: 1

Location: Germany

Data Center 2

Concurrent Users: 5,000

Applications: 3

Location: England

Data Center 1

Concurrent Users: 10,000

Applications: 26

Location: USA-West

Site 2 Site 3

Data Center 3

Concurrent Users: 200

Applications: 1

Location: USA-Central

Data Center 1

Concurrent Users: 10,000

Applications: 30

Location: USA-West

Site 1

Data Center 4

Concurrent Users: 150

Applications: 1

Location: Germany

Data Center 2

Concurrent Users: 5,000

Applications: 3

Location: England

Data Center 3

Concurrent Users: 200

Applications: 1

Location: USA-Central

Data Center 1

Concurrent Users: 20,000

Applications: 56

Location: USA-West

Site 1 Site 2

Data Center 4

Concurrent Users: 150

Applications: 1

Location: Germany

Data Center 2

Concurrent Users: 5,000

Applications: 3

Location: England

Data Center 3

Concurrent Users: 200

Applications: 1

Location: USA-Central

Data Center 1

Concurrent Users: 20,000

Applications: 56

Location: USA-West

Site 1

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Zones subdivide single sites, often associated with geographical locations. There are several factors to

consider when determining the overall topology of the XenApp and XenDesktop solution:

 Risk Tolerance – Create multiple XenDesktop sites to minimize the impact from a site-wide

outage. For example, corruption of the XenDesktop site database could affect site-wide

availability. For many organizations, the decreased risk from implementing multiple sites

outweighs the additional management overhead and supporting infrastructure required.

 Security – Although delegated administration is available, high-security organizations may

require complete separation between environments to demonstrate compliance with specific

service level agreements.

 Administrative Boundaries – Due to billing/charge back requirements or how IT is structured,

multiple sites might be required to separate administrative boundaries.

 Geographical Connectivity – Although the implementation of zones does allow a single site to

span geographical locations, there must be enough bandwidth between the satellite zone

and primary zone for the site database to capture the session information. Higher latency or

larger zones impacts response times for the user.

XenApp/XenDesktop 7.13

XenApp/XenDesktop 7.11

Latency (ms)

250

Concurrent Requests

Average Response Time

3.7

7.6

Brokering Requests per second

12.6

6.3

Time to launch 10,000 users

13 minutes

26 minutes

Table 12: Zones Brokering Performance

Session count

Max concurrent

session launches

Min site-to-site

bandwidth

Max site-to-site

round trip latency

Less than 50

1 Mpbs

250 ms

50 to 500

1.5 Mbps

100 ms

500 to 1,000

2 Mbps

50 ms

1,000 to 3,000

8 Mbps

10 ms

Experience from the Field

Finance – A large financial institution hosts 10,000 desktops from a single

datacenter. To reduce risk, it was decided that no site should exceed 5,000

desktops. Therefore, despite the desktops being connected by a fast and

redundant network, two sites were created.

Experience from the Field

Retail – A retail organization required complete separation for employees

responsible for managing financial data. To meet this requirement, two separate

sites were created within the same datacenter – one for the financial employees

and a second for all other employees.

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Over 3,000

8 Mbps

5 ms

Table 13: Zone Networking Requirements

In general, administrators should minimize the number of XenDesktop sites and zones to reduce

architectural complexity and administrative effort.

Decision: Image Management Strategy

A XenApp and XenDesktop solution requires the creation and management of master image(s).

Organizations must decide early what strategy to pursue for image management.

Installed Images

An installed image requires the administrator to install the operating system and applications for each

image. This approach is straightforward but creates a duplication of effort as the admin installs the

same operating system and core applications across multiple master images.

Maintaining master images also includes duplication of effort as the same operating system version

and core applications are part of multiple images, each requiring the same update process.

Scripted Images

Administrators can automate many of the tasks associated with installed images with scripting or

automation tools. Many operating system and application installs support automated scripting, which

mitigates the duplication of effort impact on the administrator’s time with installed images.

Unfortunately, learning, creating and maintaining a scripting framework for the entire image is

challenging and time consuming. Scripting an entire build takes time and often results in unexpected

failures if directory structures change, processes take too long to complete or a filename changes.

Layered Images

Each unique operating system (Windows 10, Windows 2012R2 and Windows 2016), platform

(XenApp/XenDesktop 7.13 VDA, XenApp/XenDesktop 7.14 VDA and XenApp/XenDesktop 7.15 VDA)

and application (Microsoft Office, Adobe Acrobat, Google Chrome and Mozilla Firefox) is a layer. A

master image is the merging of one operating system layer, one platform and many applications.

A layered image approach eliminates the duplication of effort challenges associated with installed and

scripted images. Each unique layer is available to any master image. When an application requires an

update, that layer receives the updates and all master images utilizing the layer receives the update. If

an organization requires ten unique Windows 10 images, each of the ten images shares the same

Windows 10 layer. When the administrator needs to upgrade the VDA from version 7.14 to 7.15 across

ten images, the administrator only updates a single platform layer.

Initially, the layered image approach does require more time to deploy because the administrator must

build the organization’s library of layers. However, once the layers are available, the time to maintain the

images is drastically reduced.

Layer 1: The User Layer

The top layer of the design methodology is the user layer, which each unique user group defines.

The user layer appropriately sets the overall direction for each user group’s environment. This layer

incorporates the assessment criteria for business priorities and user group requirements in order to define

effective strategies for endpoints and Citrix Receiver. These design decisions affect the flexibility and

functionality for each user group.

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Endpoint Selection

There is a variety of endpoints devices available, all with differing capabilities, including:

 Tablet based

 Laptop

 Desktop PC

 Thin client

 Smartphone

The user’s primary endpoint device must align with the overall business objectives as well as each user’s

role and associated requirements. In many circumstances, multiple endpoints may be suitable, each

offering differing capabilities.

Decision: Endpoint Ownership

In many organizations, endpoint devices are corporate owned and managed. However, more and

more organizations are now introducing bring your own device (BYOD) programs to improve

employee satisfaction, reduce costs and to simplify device management. Even if BYOD is a business

priority, it does not mean that every user should be allowed to use a personal device in the

corporate environment.

Certain user requirements, which were identified during the user segmentation, can greatly impact

the suitability of personal devices:

 Security – Users requiring a high-level of security might not be able to bring a personal

device into the secured environment for risk of data theft.

 Mobility – Users operating in a disconnected mode might not be able to use a personal

device, as the local VM desktop VDI model associated with this type of requirement can

have specific hardware requirements, or special maintenance requirements.

 Desktop loss criticality – Users with a high desktop loss criticality rating might require

redundant endpoints in the event of failure. This would require the user to have an

alternative means for connecting in the event their personal device fails, likely making these

users poor candidates for a BYOD program.

 VDI models – A personal device should not be recommended for user groups utilizing a

local VDI model like a local streamed desktop, local VM desktop or Remote PC Access.

These VDI models typically require a specific hardware configuration or installation that will

restrict device selection.

The following diagram provides guidance on when user owned devices could be used:

Figure 9: BYOD or Corporate Device

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Decision: Endpoint Lifecycle

Organizations may choose to repurpose devices in order to extend refresh cycles or to provide

overflow capacity for contract workers. Endpoints now offer more capabilities allowing them to

have longer useful lifespans. In many cases, these hardware capabilities vastly outstrip the needs of

a typical user. When coupled with the ability to virtualize application and desktop workloads, this

provides new options to administrators such as repurposing existing workstations. These options go

well beyond the simple three-year PC refresh cycle. However, the benefits of repurposing or

reallocating a workstation should be balanced against the following considerations.

 Minimum standards – While cost factors of repurposing existing workstations may be

compelling, certain minimum standards should be met to guarantee a good user

experience. At a minimum, it is recommended that repurposed workstations have a 1GHz

processor, 1GB of RAM, 16GB of free disk space and a GPU that is capable of supporting

HDX features.

 Business drivers – Priorities underpin the success of any major project. Those organizations

that have prioritized reducing capital expenditure by means of prolonging the hardware

refresh cycle can benefit from repurposing hardware. Conversely, if an organization’s

business drivers include reducing power consumption as part of an overall green initiative,

purchasing newer endpoints may be beneficial in order to take advantage of the latest

generation of power management capabilities available in the most modern devices.

 Workload – The type of work and VDI model for an end user can determine whether they

are a good candidate for a repurposed endpoint, or may be better served with a new device.

If the work performed by the individual involves locally installed applications, the individual

may be best served by a new endpoint that offers the most powerful and recently updated

processor and graphics architecture. However, if a user is largely performing tasks

associated with virtualized applications that do not involve the latest multimedia capabilities

such as webcams, VoIP and media redirection, then a repurposed workstation should be a

viable alternative.

The following planning matrix outlines considerations when repurposing existing hardware:

Endpoint Provisioning Criteria

Repurpose

Existing

Procure New

Capital restrained environment



High number of virtualized

applications



Desire to prolong hardware refresh

cycle



High failure rate among existing

desktops



Outmoded client-side feature set



Power consumption or green

initiative(s)



Table 14: Endpoint Procurement Criteria

Decision: Unified Endpoint Management (UEM)

VDI allows users to work on any device from any location while still getting access to their apps and

data. With distributed users accessing the environment across multiple devices, including mobile

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devices, administrators need to be able to centrally secure and support the mobile devices.

Administrators need to:

 Selectively wipe a device if the device is lost, stolen, or out of compliance.

 Require passcode security standards

 Define geo-location device restrictions

 Simplify Exchange ActiveSync configuration

 Define WiFi parameters for office locations

 Integrate certificates to secure communications

Managing the distributed endpoints is only part of the challenge. Administrators need to define

levels of access. Administrators need to secure and control access to the apps and data. Security

becomes a greater concern when users have access to corporate XenApp and XenDesktop

resources from personal devices. A few things to consider when delivering XenApp and XenDesktop

apps to mobile devices:

 What resources can a jailbroken device access?

 Can users copy/paste between personal apps and XenApp and XenDesktop apps?

 Can a device with no configured passcode get access to corporate resources?

 Can users continue to use a native or untrusted third party email client?

 Can mobile device users access Intranet sites with a browser optimized for mobile devices

or with a published desktop browser?

UEM Solutions, like Citrix XenMobile, protects app data and lets admins control app data sharing.

UEM also allows for the management of corporate data and resources, separately from personal

data.

Decision: Mobile Device Management (MDM)

VDI allows users to work on any device from any location while still getting access to their apps and

data. With distributed users accessing the environment across multiple devices, including mobile

devices, administrators need to be able to centrally secure and support the mobile devices, which is

knows as Mobile Device Management (MDM).

MDM solutions, like Citrix XenMobile, enables organizations to protect devices and data on devices

at a system level. For example,

 Selectively wipe a device if the device is lost, stolen, or out of compliance.

 Require passcode security standards

 Define geo-location device restrictions

 Simplify Exchange ActiveSync configuration

 Define Wi-Fi parameters for office locations

 Integrate certificates to secure communications

MDM is typically suitable for corporate-owned mobile devices because most users with personal

devices do not want to give the IT team that much control over their personal devices.

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Decision: Mobile Application Management (MAM)

With a distributed workforce accessing the XenApp and XenDesktop environment across numerous

devices, administrators need to secure and control access to the apps and data. Security becomes a

greater concern when users have access to corporate XenApp and XenDesktop resources from

personal devices. A few things to consider when delivering XenApp and XenDesktop apps to mobile

devices:

 What resources can a jailbroken device access?

 Can users copy/paste between personal apps and XenApp and XenDesktop apps?

 Can a device with no configured passcode get access to corporate resources?

 Can users continue to use a native or untrusted third party email client?

 Can mobile device users access Intranet sites with a browser optimized for mobile devices

or with a published desktop browser?

MAM solutions, like Citrix XenMobile, protects app data and lets admins control app data sharing.

MAM also allows for the management of corporate data and resources, separately from personal

data.

MAM is often suitable for bring-your-own (BYO) devices because, although the device is

unmanaged, corporate data remains protected.

Decision: Endpoint Form Factor

The capabilities of endpoints have grown along with efficiencies offered in thin client form factors.

Even mid-range thin clients now have graphics capabilities that allow utilization of HDX features

such as multi-monitor support while offering management and power efficiency benefits. Citrix has

developed a three-tiered classification for thin clients based on their HDX capabilities: HDX Ready,

HDX Premium, and HDX 3D Pro, which can be used to help narrow the field of appropriate thin

client devices based on the use case requirements. This expansion of capabilities has given IT

administrators more options and flexibility than ever before.

Most organizations will likely deploy a mixture of fully featured clients as well as thin clients.

However, certain endpoint devices are more appropriate when used in combination with certain

VDI models as explained in the following table.

VDI Model

Thin

Clients

Desktop

Laptop

Tablet

Smartphone

Hosted Windows Apps



Hosted Browser Apps



Hosted Shared Desktop



Hosted Pooled Desktop



Hosted Personal Desktop



Hosted Pro Graphics

Desktop



Local Streamed Desktop







Local VM Desktop







Remote PC Access





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“”: Recommended, ““: Not Recommended, “º” Viable

Table 15: Primary Endpoint Selection

Receiver Selection

Citrix Receiver is an easy-to-install software client that provides access to applications, desktops and

data easily and securely from any device, including smartphones, tablets, PCs and Macs.

The following section provides a series of design decisions that should be considered when deploying

Citrix Receiver.

Decision: Receiver Type

While most organizations should simply deploy the latest Citrix Receiver compatible with their

endpoint, it is important to recognize that there are certain differences between editions. The

following table should be referenced to determine the most appropriate edition of Citrix Receiver

for each user group. For the latest feature matrix, please refer to Receiver Feature Matrix.

Decision: Initial Deployment

There are several deployment options available for delivering Citrix Receiver to an endpoint.

Although it is usually a best practice to have a full version of Citrix Receiver deployed to an endpoint

to provide the greatest level of functionality, it is important to consider fallback options such as the

HTML5 Receiver for those situations where the installation of Citrix Receiver is simply not possible.

Note that although the HTML5 Receiver can be used as a fallback option, like the Java client was

with Web Interface, it is not generally recommended as the primary Receiver for enterprises to

standardize on due to the limited feature set and common browser restrictions around unsecured

WebSockets connections (see CTX134123 for more information).

Experience from the Field

Large systems integrator – A large systems integrator recommended that a customer deploy a single

type of low-end, limited capability endpoint for all users. Upon deployment to production, users

immediately complained that they received a poor user experience when viewing multimedia

content over the WAN. At great cost, the systems integrator and customer re-assessed the

environment and chose to deploy endpoints that supported HDX MediaStream. The mistake caused

a schism between systems integrator and the customer, resulting in lost time, capital and the end of

a business relationship that was fostered over many years. It is critical that the endpoints assigned to

each user group can support their requirements.

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The following mechanisms are commonly used to deploy and update Citrix Receiver:

 StoreFront – If Citrix StoreFront is available, administrators can deploy Citrix Receiver via a

Receiver for Web site by enabling the “Client Detection” feature. When deployed, a Receiver

for Web site enables users to access StoreFront stores through a web page. If the Receiver

for Web site detects that a user does not have a compatible version of Citrix Receiver, the

user is prompted to download and install Citrix Receiver. The Receiver clients can be hosted

on the StoreFront server, or users can be directed to citrix.com for the latest Receiver files.

 Internal download site – Users may be prevented from downloading software from the

Internet, even if they have permission to install applications. Administrator can create an

internal website for supported Citrix Receivers or host them on a common software

distribution point for a more seamless user experience. This could be an alternative to

enabling Client Detection on the StoreFront Receiver for Web site, which can result in an

inconsistent user experience depending on browser’s ActiveX settings.

 Markets and stores –Citrix Receiver is available on the Windows, Android and iOS stores..

 Enterprise software deployment – Many organizations employ an enterprise software

deployment (ESD) or Mobile Application Management (MAM) solution. ESD/MAM solutions

can be used to deploy Citrix Receiver to managed endpoint devices. Employee-owned

devices can only be managed if the user successfully registered the device with the

management tool.

 Master image – Most organizations have a group of master desktop images, which are

deployed to each business owned desktop, laptop, server, or virtual desktop. A common

mechanism to ensure access to virtual desktops and applications is to include a supported

version of Citrix Receiver in the master image. Subsequent updates to Citrix Receiver are

handled either by enterprise software deployment tools or manually.

 Group policy – For customers without a robust ESD solution, it is possible to deploy and

configure Citrix Receiver via Microsoft Group Policy. Sample start-up scripts that deploy and

remove Citrix Receiver are available on Citrix XenApp and XenDesktop media:

Citrix Receiver and Plugins\Windows\Receiver\Startup_Logon_Scripts

Experience from the Field

Furniture distributor – A furniture distributor maintains a configurator application for various

furniture options. The configurator application is accessed via a limited functionality kiosk that is

deployed at various furniture outlets, including small, independent retailers with little to no IT staff

present. The kiosks are completely locked down in many situations, to the point where even the

running of Java applications is limited. The kiosks do feature a modern browser (Google Chrome),

and therefore, are able to utilize the HTML5 Receiver in order to provide access to the configurator

application.

County government – A government IT organization provides services to all agencies operating in

the county. A mixture of full desktops are applications are deployed to both Windows based

desktops and iPads. Since the desktops are joined to the Active Directory domain, GPOs are utilized

to deploy and configure Citrix Receiver. Mobile users accessing the Citrix environment via an iPad

install and configure Receiver from the App Store. To allow for seamless provisioning, email based

discovery was configured. This allows users to configure Receiver for both internal and external

access through NetScaler Gateway by entering in their email address.

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 Manual install – All supported versions of Citrix Receiver are available from the Citrix

Receiver Download site. Upon landing on this site, client detection is performed and a

platform and operating system specific link is provided to allow users to download an

appropriate edition of Citrix Receiver. It is important to note that no configuration will be

accomplished via this download, so users will receive the first time use prompt to enter a

server URL or email address. This option is likely to be utilized in a BYOD environment.

Selecting the appropriate deployment method is based on the type of Citrix Receiver selected.

The following table should be referenced to help identify the appropriate deployment options

for Citrix Receiver.

Deployment Options

Thin clients

Desktop PC

Laptop

Tablet

Smartphone

Base image





ESD / MAM







Group Policy







Receiver for Web Site







Internal Download

Site







App Store





“”: Recommended, ““: Not Recommended

Table 16: Receiver Deployment Options

Decision: Initial Configuration

Citrix Receiver must be configured in order to provide access to enterprise resources. The method of

configuration varies by Citrix Receiver edition, the form factor of the device, and lastly the access

method (local or remote) that is involved. Several methods may be viable for an organization. The

method utilized is contingent on the resources (people, systems, time) available as well as larger

organizational initiatives such as BYOD programs.

The following methods can be used to configure Citrix Receiver:

 Email based discovery – The latest releases of Citrix Receiver can be configured by entering

an email address. Email based discovery requires Citrix StoreFront as well as an SRV DNS

record which points to the FQDN of the StoreFront server.

Note: Any DNS platform should support email-based discovery, however only Windows DNS

has been explicitly tested.

For remote access, NetScaler Gateway must be utilized with the corresponding SRV record

in external DNS. A valid server certificate on the NetScaler Gateway appliance or StoreFront

server must be present in order to enable email-based account discovery. This configuration

assumes that the portion of the email address after the “@” is the DNS namespace that

should be queried for this SRV record. This can be challenging for customers with different

external and internal namespaces or email addresses that are different from DNS

namespaces.

 Group policy – Microsoft Group Policy can be used to configure Citrix Receiver. This can be

done via start up scripts used to deploy Receiver by ensuring there is a value for the

SERVER_LOCATION=Server_URL parameter or by using the ADMX/ADML template files

included with the installation of Citrix Receiver to set the StoreFront Account List option in

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conjunction with another Receiver deployment method. Provide the URL of the server

running Citrix StoreFront in the format https://baseurl/Citrix/storename/discovery.

 Provisioning file – For environments running StoreFront, it is possible to provide users with a

provisioning file that contains store information. Provisioning files are exported from the

StoreFront console. The file is saved with a “*.cr” extension and can then be placed on a

shared network resource, a Receiver for Web site, or other web based resource or emailed

to users. The file can then be launched from an endpoint, which automatically configures

Citrix Receiver to use the store(s). If users browse to the Receiver for Web site and select the

“Activate” option under their username, this also automatically downloads this same “.cr” file

and configure the Receiver client for users.

 Manually – If allowed, it is usually possible to configure Citrix Receiver manually by entering

the server URL. This method should be reserved for administrators or users that have

advanced knowledge.

 Studio – In addition to the above methods, in order to configure Receiver deployed on a

virtual desktop or server image (within a XenDesktop or XenApp environment), it is possible

to set the StoreFront address via the properties of the Delivery Group.

Decision: Updates

Citrix Receiver is in active development. As such, periodic updates are released that provide

enhanced functionality or address user issues. As with any actively developed product, the latest

version of these products should be deployed to the endpoints so that users benefit from the latest

functionality and to maintain compliance with product support lifecycles. There are multiple

methods available to update Citrix Receiver and, if applicable, associated plug-ins.

 Auto-Update – Receiver for Windows 4.8+ and Receiver for Mac 12.6+ includes an auto-

update capability that automatically checks for newer versions of Receiver. The auto-

update service can be configured to allow users to defer updates as well as to skip any

updates that are not long-term service release (LTSR) versions. Receiver for iOS and Android

are automatically updated through their appropriate store.

 Enterprise software deployment – ESD tools provide an organization with direct control

over the time/frequency of Receiver updates to managed devices. Additional thought must

be given to updating unmanaged devices and endpoints outside of the corporate firewall.

 Manual updates – When no automated solution is available, manual methods can be used

to update Citrix Receiver. Whether deployed on Receiver for Web site, StoreFront, an

internal Citrix Receiver site, or an external site, these options will require user involvement in

updating Citrix Receiver. Due to the involved nature of manual updates coupled with the

opportunity for a user mistake, this option should only be considered as a last resort.

Layer 2: The Access Layer

The second layer of the design methodology is the access layer, which is defined for each user group.

Creating an appropriate design for the access layer is an important part of the desktop virtualization

process. This layer handles user validation through authentication and orchestrates access to all

components necessary to establish a secure virtual desktop connection.

The access layer design decisions are based on the mobility requirements of each user group as well as the

endpoint devices used.

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Authentication

Getting access to resources is based on the user’s identity. Defining the authentication strategy

takes into account the user’s entry point into the environment as well as how the user will

authenticate.

Decision: Authentication Provider

Traditionally, users required an Active Directory username and password to get access to their

XenApp and XenDesktop resources. As most organizations standardized on an on-premises Active

Directory deployment, this particular requirement was simple to achieve.

Organizations are using external contractors, which requires an account to get access to the

XenApp and XenDesktop resources. Organizations are investigating the use of a third party identity

provider (IdP) like Azure Active Directory, Google, LinkedIn, etc., instead of managing their own.

With the implementation of Citrix Federated Authentication Service, XenApp and XenDesktop

supports the use of a third party IdP. An administrator can have a contractor use their Google

account to gain access to their approved applications and desktops, simplifying onboarding.

Decision: Authentication Point

Before a user connects to a virtual resource, they must first authenticate. The place of

authentication is often determined by the user group’s mobility requirements, which were

defined during the user segmentation process. There are two authentication points available in

XenDesktop:

 StoreFront – Citrix StoreFront provides authentication and resource delivery services for

Citrix Receiver, enabling centralized enterprise stores to deliver desktops, applications

and other resources.

 NetScaler Gateway – NetScaler Gateway is an appliance providing secure application

access and granular application-level policy controls to applications and data while

allowing users to work from anywhere.

The following table lists preferred authentication points according to user group mobility

requirements:

User Group’s Mobility Requirement

Preferred Authentication Point

Local

StoreFront

Roaming local

StoreFront

Remote

NetScaler Gateway

Mobile

NetScaler Gateway

Table 17: Preferred Authentication Point

Authentication for user groups with a mobility requirement of remote or mobile may occur

directly on StoreFront where required. For example, DMZ security policies may prohibit access

from the NetScaler Gateway to the domain, which is required to support Smartcard client

certificate authentication. Access to StoreFront for authentication may then be delivered via a

NetScaler SSL_BRIDGE virtual server, which provides a conduit for https traffic. Typically, the

virtual server would be hosted alongside a NetScaler Gateway on the same NetScaler configured

to provide HDX Proxy access to the virtual desktop environment. Although such a use case may

sometimes be necessary, the recommended best practice is to authenticate external users via

NetScaler Gateway.

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Decision: Authentication Policy

Once the authentication point has been identified, the type of authentication must be

determined. The following options are the primary methods available:

 StoreFront – Supports a number of different authentication methods, although not all

are recommended depending on the user access method, security requirements and

network location. Note that by default StoreFront authenticates users directly with Active

Directory, not via XML as Web Interface did. StoreFront 3.0+ can be optionally

configured to delegate authentication to XML if required (such as if the StoreFront

servers are in a domain that does not trust the user domains).

o User name and password – Requires users to logon directly to the site by

entering a user name and password.

o Domain pass-through – Allows pass-through of domain credentials from users'

devices. Users authenticate to their domain-joined Windows computers and are

automatically logged on when they access their stores.

o NetScaler Gateway pass-through – Allows pass-through authentication from

NetScaler Gateway. Users authenticate to NetScaler Gateway and are

automatically logged on when they access their stores.

o Smart card – Allows users to authenticate using smart cards and PINs through

Citrix Receiver for Windows and NetScaler Gateway. To enable smart card

authentication, user accounts must be configured either within the Microsoft

Active Directory domain containing the StoreFront servers or within a domain

that has a direct two-way trust relationship with the StoreFront server domain.

Multi-forest deployments involving one-way trust or trust relationships of

different types are not supported.

o Anonymous – Allow users to access applications and desktops without

presenting credentials to StoreFront or Citrix Receiver. Local anonymous

accounts are created on demand on the Server VDA when sessions are

launched. This requires a StoreFront store configured for authenticated access, a

Server OS based VDA, and a XenApp Delivery Group configured for

unauthenticated users.

 NetScaler Gateway – The NetScaler Gateway supports several authentication methods.

The list below includes those primarily used in virtual desktop environments. Each may

be used individually, but are often combined to provide multi-factor authentication.

o LDAP – The lightweight directory access protocol (LDAP) is used to access

directory information services such Microsoft Active Directory. NetScaler

Gateway uses LDAP to authenticate users and extract their group membership

information.

o RADIUS (token) – Remote authentication dial in user service (RADIUS) is a UDP

based network security protocol that provides authentication, authorization and

accounting. A network access server (NetScaler Gateway in this case) forwards

credentials to a RADIUS server that can either check the credentials locally, or

check them against a directory service. The RADIUS server could then accept the

connection, reject the connection, or challenge and request a second form of

authentication such as a token.

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o Client certificate – Users logging on to a NetScaler Gateway virtual server can

also be authenticated based on the attributes of a client certificate presented to

the virtual server. Client certificates are usually disseminated to users in the form

of smartcards or common access cards (CACs) that are read by a reader attach

to each user’s device.

The authentication type for a user group is often determined based on security requirements as

well as the authentication point used. The following table helps define the appropriate solution

for each user group based on the level of security required:

Authentication Point

Security Requirement

Authentication Type

StoreFront

Low

 LDAP Username and Password

 Pass-through

Medium

 LDAP Username and Password

 Pass-through

High

 LDAP and/or Smartcard

NetScaler Gateway

Low

 LDAP Username and Password

Medium

 LDAP Username and Password

High

 LDAP and Token

 LDAP and Smartcard

 Token and Smartcard

Table 18: Authentication Policy Guidance

Experience from the Field

Retail – A small private retail company provides virtual desktop users with access to non-sensitive

data such as marketing catalogs and email. They are not required to adhere to security

regulations such as Sarbanes Oxley. Therefore, LDAP authentication has been implemented

based on user name and password.

Financial – A medium financial enterprise provides their virtual desktop users with access to

confidential data such as banking transaction records. They are governed by security regulations

such as the Statement on Accounting Standards (SAS) 70 and are required to utilize multi-factor

authentication for remote access users. LDAP authentication has been implemented based on

user name and password along with RADIUS authentication using tokens.

Government – A large federal institution provides virtual desktop users with access to highly

confidential data such as private citizens’ personal records. They are subject to regulation by

Department of Defense (DOD) security standards. LDAP authentication has been implemented

based on user name and password, along with Client Certificate authentication using CAC cards.

Healthcare - A hospital is using XenApp to deliver their EMR application to users. ThinClient

devices on stationary and mobile carts are being used by doctors and nurses to capture and

retrieve patient data. Unauthenticated access has been configured to prevent medical staff from

having to authenticate to the domain as well as the EMR application.

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StoreFront

Citrix StoreFront authenticates users to XenApp and XenDesktop resources. StoreFront enumerates

and aggregates available desktops and applications into a single interface that users access through

Citrix Receiver for Windows, iOS, Android, or the StoreFront web site.

Decision: High Availability

If the server hosting StoreFront is unavailable, users will not be able to launch new virtual desktops,

published applications or manage their subscriptions. Therefore at least two StoreFront servers

should be deployed to prevent this component from becoming a single point of failure. By

implementing a load balancing solution, users will not experience an interruption in their service.

Options include:

 Hardware load balancing – An intelligent appliance, which is capable of verifying the

availability of the StoreFront service and actively load balance user requests appropriately.

Citrix NetScaler is a great example of a hardware load balancer. Citrix NetScaler is an ideal

load balancer, coming pre-configured with StoreFront health checks.

 DNS round robin – Provides rudimentary load balancing across multiple servers without

performing any checks on availability. If a StoreFront server becomes unavailable, DNS

round robin would still route users to the failed server. Because of this, DNS round robin is

not recommended by Citrix.

 Windows network load balancing – A Windows service capable of performing

rudimentary checks to verify the server is available but cannot determine the status of

individual services. This can cause users to be forwarded to StoreFront servers which are

not able to process new requests. The user would then not be able to access applications

or desktops.

Decision: Delivery Controller Reference

To provide users with desktops and applications, StoreFront must be configured with the IP

address or DNS name of at least one Controller in each XenDesktop and XenApp site. For fault

tolerance, multiple controllers should be entered for each site and/or farm specified. By default,

StoreFront treats a list of servers in failover order (active/passive).

For large deployments or environments with a high logon load an active distribution of the user

load (active/active) is recommended. This can be achieved by means of a load balancer with

built-in XML monitors, such as Citrix NetScaler or by configuring StoreFront to load balance the

list of Controllers instead of treating them as an ordered list.

Decision: Beacons

Citrix Receiver uses beacons (websites) to identify whether a user is connected to an internal or

external network. Internal users are connected directly to StoreFront for authentication while

external users are connected via Citrix NetScaler Gateway. It is possible to control what a user

sees by restricting applications due to which beacon they have access to.

The internal beacon should be a site that is not resolvable externally. By default, the internal

beacon is the StoreFront base URL. This will have to be adjusted if the same external and internal

URL is configured. The external beacon can be any external site that produces an http response.

Citrix Receiver continuously monitors the status of network connections (for example, link up,

link down or change of the default gateway). When a status change is detected, Citrix Receiver

first verifies that the internal beacon points can be accessed before moving on to check the

accessibility of external beacon points. StoreFront provides Citrix Receiver with the http(s)

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addresses of the beacon points during the initial connection/configuration download process

and provides updates as necessary.

It is necessary to specify at least two highly available external beacons that can be resolved from

public networks.

Decision: Resource Presentation

By default, StoreFront allows users to choose (subscribe) to the resources they want to regularly

use after they logon (favorites). This approach, deemed “Self-Service,” allows users to restrict the

resources that they see on their home screen to the ones that they use on a regular basis. The

resources chosen by every user for each store are recorded by the subscription store service and

stored locally on each StoreFront server (synced automatically between servers in the same

server group) so that they can be displayed on the Citrix Receiver home screen from any device

that the user connects from. Although by default subscriptions are per store and per server

group, administrators can configure two stores within a server group to share a subscription

database and/or sync subscriptions between two identically named stores in two separate server

groups on a defined schedule if required.

Administrators should determine which applications should always be displayed to users on their

home screen or the featured tab. In general, these applications are common applications such as

the Microsoft Office Suite and any other applications that every user in an environment may

need. StoreFront can filter/present these resources using Keywords defined within the published

application properties Description field.

The following table explores the Keyword options:

Keyword

Description

Auto

Automatically subscribes all users of a store to an application. When users

log on to the store, the application is automatically provisioned without

users needing to manually subscribe to the application. Users can choose

to subsequently remove this subscription if desired.

Mandatory

New in StoreFront 2.5, the Mandatory keyword will make applications

automatically be subscribed to users of the store. However, users will not

have the option to remove the application. This setting is useful when

creating a core set of applications which must always be presented to all

users.

Featured

Advertise applications to users or make commonly used applications easier

to find by listing them in the Receiver Featured list.

Prefer

Specify a locally installed application should be used instead of an

application available in Receiver.

Receiver searches for the specified name/path to determine if the

application is installed locally. If it is, Receiver subscribes the application

and does not create a shortcut. When the user starts the application from

the Receiver window, Receiver starts the locally installed (preferred)

application.

If a user uninstalls a preferred application outside of Receiver, the

application is unsubscribed during the next Receiver refresh. If a user

uninstalls a preferred application from the Receiver window, Receiver

unsubscribes the application but does not uninstall it.

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TreatAsApp

By default, XenDesktop VDI desktops and XenApp hosted shared desktops

are treated like other desktops by Receiver for Web sites. By using the

keyword “TreatAsApp,” the desktop will be displayed in the application

views of Receiver for Web sites rather than the desktop views. Users are

required to subscribe before they can access the desktop.

Primary

When in a multi-site deployment, using this keyword ensures that an

application is delivered from a designated site. If an application is available

from multiple sites, with the same name, the application from the

secondary site will only be displayed if the application is not available from

the primary site.

Secondary

A same property as the “Primary” keyword, except it designates an

application in the secondary site.

Table 19: Keywords for Application Delivery

Decision: Aggregation Groups

If the XenApp/XenDesktop solution includes multiple delivery sites, StoreFront merges the

available resources together so the user has a single interface for all published resources.

However, if multiple sites publish the same resources, the user might experience confusion as a

single application appears multiple times.

Figure 10: User experience without aggregation

StoreFront aggregation groups define how the resources in multiple sites merge to provide the

user with a single, easy to understand view. StoreFront aggregates duplicate published

resources into a single icon.

Figure 11: User experience with aggregation

The administrator must determine how to load balance users across the different

XenApp/XenDesktop sites when the icon is an aggregation. The options are:

 Load Balancing – Used when the duplicate sites are created based on capacity

recommendations. StoreFront distributes user requests across all configured sites.

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 Failover – Used when geographies need to have resources available in the event of an

outage or when migrating users from one site to another site (like a XenApp migration

project).

It is advisable to document the users, stores and aggregation methods during the design phase.

User Group

Available Store(s)

Load Balancing Stores

Failover Stores

NA_FinanceUsers

NA_West_Store

NA_East_Store

EMEA_Store

NA_West_Store

NA_East_Store

EMEA_Store

EMEA_SalesUsers

EMEA_Store

NA_East_Store

EMEA_Store

NA_East_Store

Table 20: Aggregation Groups

Decision: Scalability

The number of Citrix Receiver users supported by a single StoreFront server depends on the

resources assigned and level of user activity. Note that Receiver for Web users will consume

more RAM on average than native Receiver users, but a minimum of 4 GB of RAM is

recommended per StoreFront server in all cases as a baseline. Additionally, more sites/farms

enumerated per store will increase both CPU utilization and server response time, with XenApp

IMA farms having a greater scalability impact than XenApp/XenDesktop FMA site.

StoreFront deployment

CPU Usage

Simultaneous activities

 Standalone deployment

 4 CPUs

 4 GB RAM

 Heavy Usage (logon, enumerate,

subscribe, unsubscribe, logoff)

75%

 291 per second

90%

 375 per second

 Cluster StoreFront deployment

 2 Nodes each with:

o 4 CPUs

o 4 GB RAM

o Heavy Usage (logon, enumerate,

subscribe, unsubscribe, logoff)

75%

 529 per second

90%

 681 per second

Table 21: StoreFront Scalability

Tests have shown diminishing returns after a single StoreFront deployment grows beyond 3-4

StoreFront nodes with a maximum of 5-6 servers supported in a single server group.

NetScaler Gateway

User groups utilizing NetScaler Gateway as their authentication point have additional design

decisions to consider. These design decisions are not applicable for non-NetScaler Gateway

authentication points.

Decision: Topology

Selection of the network topology is central to planning the remote access architecture to

ensure that it can support the necessary functionality, performance and security. The design of

the remote access architecture should be completed in collaboration with the security team to

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ensure adherence to corporate security requirements. There are two primary topologies to

consider, each of which provides increasing levels of security:

 1-Arm (normal security) – With a 1-arm topology, the NetScaler Gateway utilizes one

physical or logical bonded interface, with associated VLAN and IP subnet, to transport

both frontend traffic for users and backend traffic for the virtual desktop infrastructure

servers and services.

Figure 12: 1-Arm Topology

 2-Arm (high security) – With a 2-arm topology, the NetScaler Gateway utilizes two or

more physically or logically bonded interfaces, with associated VLANS and IP subnets.

Transport of the frontend traffic for users is directed to one of these interfaces. The

frontend traffic is isolated from backend traffic, between the virtual desktop

infrastructure servers and services, which is directed to a second interface. This allows

the use of separate demilitarized zones (DMZs) to isolate frontend and backend traffic

flows along with granular firewall control and monitoring.

Figure 13: 2-Arm Topology

Decision: High Availability

If the NetScaler Gateway is unavailable, remote users will not be able to access the environment.

Therefore at least two NetScaler Gateway hosts should be deployed to prevent this component

from becoming a single point of failure.

Datacenter

*Port 80 used for

https redirect

DMZ

Firewall

(UDP)

389/636

(TCP)

443, 80 (HTTP\TCP)

3010, 3008, 22 (TCP)

Corp. Infrastructure

DNS

LDAP/

LDAPS

Internal Devices

Internet

443/80*

(HTTP/TCP)

Remote End Users

External Devices

NetScaler

Administration

Citrix Infrastructure

XenDesktop

Controller

LDAP/

LDAPS

StoreFront

STA

StoreFront

Callback

80, 8080, 443 (HTTP\TCP)

1494, 2598 (TCP)

NetScaler

Gateway

Datacenter

*Port 80 used for

https redirect

DMZ

Firewall

(UDP)

389/636

(TCP)

443, 80 (HTTP\TCP)

3010, 3008, 22 (TCP)

Corp. Infrastructure

DNS

LDAP/

LDAPS

Internal Devices

Internet

443/80*

(HTTP/TCP)

Remote End Users

External Devices

NetScaler

Administration

Citrix Infrastructure

XenDesktop

Controller

LDAP/

LDAPS

StoreFront

STA

XenApp

Controller

StoreFront

Callback

80, 8080, 443 (HTTP\TCP)

1494, 2598 (TCP)

NetScaler

Gateway

DMZ

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When configuring NetScaler Gateway in a high availability (active/passive) pair, the secondary

NetScaler Gateway monitors the first appliance by sending periodic messages, also called a

heartbeat message or health check, to determine if the first appliance is accepting connections.

If a health check fails, the secondary NetScaler Gateway tries the connection again for a specified

amount of time until it determines that the primary appliance is not working. If the secondary

appliance confirms the health check failure, the secondary NetScaler Gateway takes over for the

primary NetScaler Gateway.

Note that in firmware 10.5 and above, clustering is also possible with multiple NetScaler Gateway

instances to provide high availability, although support for spotted versus stripped

configurations varies by firmware and Gateway configuration (full SSL VPN versus ICA proxy).

(http://docs.citrix.com/en-us/netscaler/11-1/clustering/cluster-features-supported.html)

Decision: Platform

In order to identify an appropriate NetScaler platform to meet project requirements, the key

resource constraints must be identified. Since all remote access traffic will be secured using the

secure sockets layer (SSL), transported by Hypertext Transfer Protocol (HTTP) in the form of

HTTPs, there are two resource metrics that should be targeted:

 SSL throughput – The SSL throughput is the gigabits of SSL traffic that may be processed

per second (Gbps).

 SSL transactions per second (TPS) – The TPS metric identifies how many times per

second an Application Delivery Controller (ADC) may execute an SSL transaction. The

capacity varies primarily by the key length required. TPS capacity is primarily a

consideration during the negotiation phase when SSL is first setup and it is less of a

factor in the bulk encryption / decryption phase, which is the majority of the session life.

While TPS is an important metric to monitor, field experience has shown that SSL

throughput is the most significant factor in identifying the appropriate NetScaler

Gateway.

The SSL bandwidth overhead average is often considered negligible relative to the volume of

virtual desktop traffic and is not typically accounted for as part of required SSL throughput.

However, making provisions for SSL bandwidth will help ensure the total throughput estimated

is sufficient. The fixed bandwidth added to packet headers can vary according to the encryption

algorithms used and the overall percentage of bandwidth may vary widely according to packet

size. Ideally, the overhead should be measured during a proof of concept or pilot. However, in

the absence of such data incrementing the workload bandwidth by 2% is a reasonable rule of

thumb. Therefore, to determine the SSL throughput required by a NetScaler platform, multiply

the maximum concurrent bandwidth for a datacenter by 1.02:

    

For example, assuming 128Mbps maximum concurrent bandwidth, the appropriate NetScaler

model can be determined as follows:

    

The SSL throughput value should be compared to the throughput capabilities of various

NetScaler platforms to determine the most appropriate one for the environment. There are three

main platform groups available, each of which provides broad scalability options.

 VPX – A NetScaler VPX device provides the same full functionality as hardware NetScaler.

However, NetScaler VPXs can leverage ‘off the shelf’ servers for hosting and are suitable

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for small to medium sized environments. Typically, organizations create a baseline cap

for the VPX instances at 500 users.

 MPX – A NetScaler MPX is the hardware version of the NetScaler devices. The MPX

device is more powerful than the virtual NetScaler and can support network

optimizations for larger scale enterprise deployments, particularly when SSL offload will

be configured as this is done in software on the VPX versus dedicated SSL chips on the

MPX.

 SDX – A NetScaler SDX is a blend between the virtual and physical NetScaler devices. An

SDX machine is a physical device capable of hosting multiple virtual NetScaler devices.

This consolidation of devices aids with reducing required shelf space and device

consolidation. NetScaler SDXs are suitable for handling network communications for

large enterprise deployments and/or multi-tenant hosting providers.

SSL throughput capabilities of the NetScaler platforms may be found in the Citrix NetScaler data

sheet. Therefore, based on the example calculation above, a NetScaler MPX 5550 appliance

would be sufficient to handle the required load. However, actually scalability will depend on

security requirements. NetScaler SSL throughput decreases with the use of increasingly complex

encryption algorithms and longer key lengths. Also, this calculation represents a single primary

NetScaler. At a minimum, N+1 redundancy is recommended which would call for an additional

NetScaler of the identical platform and model.

Note: The Citrix NetScaler data sheet typically represents throughput capabilities under optimal

conditions for performance. However, performance is directly affected by security requirements.

For example, if the RC4 encryption algorithm and a 1k key length are used, a VPX platform may

be able to handle more than 500 HDX proxy connections. However, if a 3DES encryption

algorithm and 2k key length are used (which are becoming more common), the throughput may

be halved.

Decision: Pre-Authentication Policy

An optional pre-authentication policy may be applied to user groups with NetScaler Gateway as

their authentication point. Pre-authentication policies limit access to the environment based on

whether the endpoint meets certain criteria through Endpoint Analysis (EPA) Scans.

Pre-authentication access policies can be configured to test antivirus, firewall, operating system,

or even registry settings. These policies can be used to prevent access entirely or can be used by

XenDesktop to control session features such as clipboard mapping, printer mapping and even

the availability of specific applications and desktops. For example, if a user device does not have

antivirus installed, a filter can be set to hide sensitive applications.

The following figure provides an overview of how multiple policies can be used to customize the

features of a virtualization resource:

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Figure 14: Simplified SmartAccess Decision Logic

Decision: Session Policy

User groups with NetScaler Gateway as their authentication point must have corresponding

session policies defined. Session policies are used to define the overall user experience post-

authentication.

Organizations create sessions policies based on the type of Citrix Receiver used. For the purpose

of session policy assignment, devices are commonly grouped as either non-mobile (such as

Windows, Mac and Linux OS based), or mobile (such as iOS or Android). Therefore, a decision on

whether to provide support for mobile devices, non-mobile devices, or both should be made

based on client device requirements identified during the assess phase.

To identify devices session policies, include expressions such as (http://docs.citrix.com/en-

us/netscaler-gateway/11-1/storefront-integration/ng-clg-session-policies-overview-con.html):

 Mobile devices – The expression is set to REQ.HTTP.HEADER User-Agent CONTAINS

CitrixReceiver which is given a higher priority than the non-mobile device policy to

ensure mobile devices are matched while non-mobile devices are not.

 Non-mobile devices – The expression is set to ns_true which signifies that it should apply

to all traffic that is sent to it.

Experience from the Field

Retail – A small private retail company use EPA to scan for the presence of updated antivirus

definitions prior to allowing access.

Financial – A medium financial enterprise use EPA scans of the Domain SID to verify that users are

members of the enterprise domain prior to allowing access.

Government – A large federal institution use EPA to scan endpoint devices to ensure that a

specific certificate (or set of certificates) has been installed on the device prior to allowing access.

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An alternative use of session policies is to apply endpoint analysis expressions. These session

policies are applied post authentication yet mimic the previously mentioned pre-authentication

policies. Use of session policies is an option to provide a fallback scenario to endpoints that do

not meet full security requirements such read-only access to specific applications.

Decision: Session Profile

Each session policy must have a corresponding session profile defined. The session profile

defines details required for the user group to gain access to the environment. There are two

primary forms of session profiles that determine the access method to the virtual desktop

environment:

 SSLVPN – Users create a virtual private network and tunnel all traffic configured by IP

addresses through the internal network. The user’s client device is able to access

permitted intranet resources as if it were on the internal network. This includes

XenDesktop sites and any other internal traffic such as file shares or intranet websites.

This is considered a potentially less secure access method since network ports and

routes to services outside of the virtual desktop infrastructure may be opened leaving

the enterprise susceptible to risks that may come with full VPN access. These risks may

include denial of service attacks, attempts at hacking internal servers, or any other form

of malicious activity that may be launched from malware, Trojan horses, or other viruses

via an Internet based client against vulnerable enterprise services via routes and ports.

Another decision to consider when SSLVPN is required is whether to enable split

tunneling for client network traffic. By enabling split tunneling, client network traffic

directed to the intranet by Citrix Receiver may be limited to routes and ports associated

with specific services. By disabling split tunneling, all client network traffic is directed to

the intranet, therefore both traffic destined for internal services as well as traffic destined

for the external services (Internet) traverses the corporate network. The advantage of

enabling split tunneling is that exposure of the corporate network is limited and network

bandwidth is conserved. The advantage of disabling split tunneling is that client traffic

may be monitored or controlled through systems such as web filters or intrusion

detection systems.

Figure 15: SSL VPN

 HDX proxy – With HDX Proxy, users connect to their virtual desktops and applications

through the NetScaler Gateway without exposing internal addresses externally. In this

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configuration, the NetScaler Gateway acts as a micro VPN and only handles HDX traffic.

Other types of traffic on the client’s endpoint device, such as private mail or personal

Internet traffic do not use the NetScaler Gateway.

Based on the endpoint and Citrix Receiver used, a decision must be made as to whether

this method is supported for each user group. HDX Proxy is considered a secure access

method for remote virtual desktop access since only traffic specific to the desktop

session is allowed to pass through to the corporate infrastructure. Most Citrix Receivers

support HDX Proxy and it is the preferred method:

Figure 16: HDX Proxy

Decision: Preferred Datacenter

Enterprises often have multiple active datacenters providing high availability for mission critical

applications. Some virtual desktops or applications may fall into that category while others may

only be accessed from a specific preferred datacenter. Therefore, the initial NetScaler Gateway

that a user authenticates to in a multi-active datacenter environment may not be within the

preferred datacenter corresponding to the user’s VDI resources. StoreFront is able to determine

the location of the user’s assigned resources and direct the HDX session to those resources;

however, the resulting path may be sub-optional (WAN connection from the NetScaler Gateway

to the virtual desktop/application resources as opposed to LAN connection).

There are static and dynamic methods available to direct HDX sessions to their virtual desktop

resources in their primary datacenter. The decision regarding which method to select should be

based on the availability of technology to dynamically assign sites links such as Global Server

Load Balancing (GSLB) along with the network assessment of intranet and Internet bandwidth as

well as Quality of Service (QoS) capabilities.

Note: For more information on configuring the static and dynamic methods of GSLB, please refer

to Citrix Product Documentation - Configuring GSLB for Proximity.

 Static

o Direct – The user may be given a FQDN mapped to an A record that is dedicated

to the primary datacenter NetScaler Gateway(s) allowing them to access their

virtual desktop directly wherever they are in the world. This approach eliminates

a layer of complexity added with dynamic allocation. However, it also eliminates

fault tolerance options such as the ability to access the virtual desktop through

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an alternative intranet path when a primary datacenter outage is limited to the

access infrastructure.

 Dynamic

o Intranet – For most dynamic environments, the initial datacenter selected for

authentication is the one closest to the user. Protocols such as GSLB dynamic

proximity calculate the least latency between the user’s local DNS server and the

NetScaler Gateway. Thereafter, by default, the HDX session is routed through

the same NetScaler Gateway to whichever datacenter is hosting the user’s virtual

desktops and applications. The advantage of this approach is that the majority

of the HDX session would traverse the corporate WAN where quality of service

may be used.

Figure 17: Intranet Connection

o Internet - Alternatively, the HDX session can be re-routed through an alternate

NetScaler Gateway proximate to the backend VDI desktop / XenApp server,

resulting in most of the HDX session travelling over the Internet. For example, a

user with a dedicated desktop in the United Stated, traveling in Europe may be

directed to a NetScaler Gateway hosted in a European datacenter based on

proximity. However, when the user launches their desktop, an HDX connection

will be established to the virtual desktop via a NetScaler Gateway hosted in the

preferred datacenter in the United States.

This conserves WAN network usage (at the cost of QoS) and is recommended in

cases where the user’s Internet connection may provide a more reliable

experience than the corporate WAN.

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Figure 18: Internet Connection

Some customers will use a combination of these methods, such as geo-specific dynamic URLs

such that fault tolerance is provided within a geographic area (such as North America) without

incurring the complexity of global GSLB.

Site-to-Site Connectivity

A XenApp and XenDesktop site is capable of spanning multiple locations, In order to successfully

implement a multi-site solution, the design must take into account the site-to-site links and XenApp

and XenDesktop session routing between locations in order to provide the best user experience.

Decision: HDX Optimized Routing

In a multi-site XenApp and XenDesktop solution, certain criteria, like fastest response time or

closest proximity, routes users to the optimal site. These algorithms do not take into account the

resources a user wants to access.

Improper routing of a user’s session results in the following:

Figure 19: HDX Optimized Routing – Not Optimized

1. User routed to the most preferred site, based on proximity or response time

Corporate WAN

User

Site 2

NetScaler Gateway

Apps and Desktops

Site 1

NetScaler Gateway

Apps and Desktops

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2. NetScaler Gateway proxies the ICA traffic to the correct resource, which could be across

the corporate WAN.

Ideally, optimized routing should resemble the following:

Figure 20: HDX Optimized Routing - Optimized

1. User routed to the most preferred site, based on proximity or response time

2. Based on the selected resource, NetScaler Gateway reroutes the session to a NetScaler

Gateway in the preferred site.

3. NetScaler Gateway proxies the ICA traffic to the correct resource, which stays on the

local LAN.

Using the optimized HDX routing option within StoreFront offloads traffic from the corporate

WAN and places it on the public network.

Decision: Virtual WAN

In branch office scenarios, a XenApp and XenDesktop design must evaluate the branch office’s

connection to the data centers hosting the application and desktop resources. If the WAN

connection between the branch office and data center is not able to meet the user

requirements, the overall user experience degrades.

Organizations have a couple of options on their WAN connections:

 Scale Up – Organizations can simply increase the size of the WAN pipe connecting the

branch offices to the data center, typically at a sizable cost.

 Scale Out – Organizations can maintain their current WAN connection and augment it

with multiple low-cost alternatives. The integration of all connections between the

branch office and data center creates a software defined virtual WAN, like NetScaler SD-

WAN. The appliance sends duplicate network packets across all WAN connections

defined within the virtual WAN. The appliance on the other end of the WAN uses the

first arriving packet, discarding all subsequent packets. As the conditions of the multiple

links change throughout the day, this approach guarantees the best experience possible.

Corporate WAN

User

Site 2

NetScaler Gateway

Apps and Desktops

Site 1

NetScaler Gateway

Apps and Desktops

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Figure 21: NetScaler SD-WAN

Broadband Circuit

MPLS Circuit

Branch Office A

NetScaler SD-WAN

Data Center

User

Apps /

Desktops

Software Defined WAN

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Layer 3: The Resource Layer

The resource layer is the third layer of the design methodology and the final layer focused specifically on

the user groups.

The overall user acceptance of the solution is defined by the decisions made within the resource layer.

Profiles, printing, applications and overall desktop image design play a pivotal role in how well the desktop

is aligned with the user group’s requirements, which were identified within the assess phase.

User Experience

Perception is everything when it comes to a good VDI experience. Users expect an experience

similar to or better than that of a traditional, physical desktop.

Codecs, transport protocols and self-service capabilities affects the overall experience. Poor quality

graphics, lagging video or 120 second logon times can destroy the user experience. A proper user

experience design can meet any network challenge.

Decision: Display Protocol

Selecting the correct display protocol determines the quality of static images, video and text

within the user’s session as well as determining the impact on single server scalability.

Administrators have the following options:

 Legacy - optimized for Windows 7 and Windows 2008R2 graphic engines (GDI/GDI+).

 Desktop Composition Redirection – offloads desktop Windows manager DirectX

commands to the endpoint, but only supports a Windows desktop VDA. Plus, in the 7.15

LTSR release, Desktop Composition Redirection is a depreciated feature.

 Framehawk – a UDP-based protocol that is able to provide high refresh rates in

environments with high latency and high packet loss scenarios at the cost of greater

network bandwidth utilization, commonly found on broadband wireless connections.

 H.264 – Often referred as the video codec, which provides the highest frame rates

required for high quality video while saving network bandwidth. It does come at the

expense of CPU processing time, reducing single server scalability. H.264 is the preferred

codec when users predominately use multimedia applications.

 Thinwire – Based on the original Citrix patents from the 1990s that thinly transfers data

over a wire. Use Thinwire in the majority of use cases as it provides a good user

experience with minimal resource costs. There are two variations of Thinwire

o Legacy - optimized for Windows 7 and Windows 2008R2 graphic engines

(GDI/GDI+).

o Thinwire+ - optimized for Desktop Windows Manager (DWM) graphics engine

in Windows 8, Windows 10, Windows 2012 and Windows 2016

 Selective H.264 (Adaptive Display) - utilizes multiple codecs (H.264 and Thinwire+)

simultaneously for portions of the screen

 Do not use – only uses Thinwire+ and not H.264. Best for users without server-

rendered video or other graphically intense applications.

 For entire screen – Only uses H.264. Best for users with heavy use of server-rendered

video and 3D graphics, especially in low-bandwidth situations.

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 For actively changing regions – Uses H.264 for the portions of the screen that are

constantly changing while the remainder of the screen uses Thinwire+. This is the best

option for most users.

Selecting the right codec not only has an impact on the overall user experience, but also on the

scalability of the server.

Figure 22: Codec Single Server Scalability

Decision: Transport Protocol

There are three ways to transport the HDX protocol across the network:

 TCP – Uses the industry standard TCP transport protocol. Common transport protocol

over LAN and low-latency WAN connections, but suffers when connection distances

increases, thus increasing latency and incurring more retransmissions.

 EDT – Uses a Citrix proprietary transport protocol called Enlightened Data Transport,

based on UDP. Meant for high latency/packet loss networks, most common on long-

distance WAN links. Provides a more interactive experience for the user without

increasing CPU load on the server, but consumes more network bandwidth than TCP.

 Adaptive Transport – Uses TCP and EDT transport protocols. EDT used unless the

network does not support transporting EDT over the network, which then automatically

changes to TCP.

Most environments will use Adaptive Transport as the standard transport option unless the

network does not have the appropriate firewall ports opened or NetScaler Gateway configured

appropriately.

Decision: Logon Optimization

Every time a user logs onto a XenApp/XenDesktop session, the logon process must complete,

which includes session initialization, user profile loading, group policy preferences execution,

drive mapping, printer mapping, logon script execution and desktop initialization. Each process

takes time and increases logon duration.

Most organizations include many mappings and complex logon scripts. When each of these

items executes, the logon time drastically increases.

100

Percent

Codec Impact on Single Server Scalability

Framehawk H.264 Selective H.264 Thinwire+

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Figure 23: Logon Script Duration

Workspace Environment Management removes drive mappings, printer mappings, logon scripts

and roaming profiles from the standard logon process. With logon optimization, Workspace

Environment Management applies the mappings/scripts/profiles in the background after the

session and desktop initializes. The user receives the same environment but they receive their

desktop interface faster. To learn more, review the following Logon Optimization video.

Most environments should enable logon optimization as a default configuration.

Decision: User Self Service

Self-service allows users to modify, update and troubleshoot their environments on their own

without requiring help desktop intervention. Most organizations have policies in place that

require users to change their passwords every 60-90 days. When users have multiple endpoint

devices with saved passwords, it is extremely easy for their account to be locked out until each

device is updated.

With StoreFront, can save time by self-servicing their own accounts with the following

capabilities:

 Account Unlock – When the user’s account is locked due to too many failed logon

attempts, common with multiple devices, they can unlock their account if they know

answers to their security questions.

 Password Reset – When users forgot their newly created password, they can reset their

password if they know the answers to their security questions.

The self-service password reset architecture introduces the SSPR Service, Central Store and two

accounts:

 Data Proxy Account – Responsible for accessing the central store, which contains

encrypted answers to the user’s security questions.

 Self Service Account – An Active Directory account with password reset and account

unlock rights.

Baseline Drive Mappings Printer

Mappings

Logon Scripts Roaming Profile

Seconds

Logon Time

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Figure 24: SSPR Architecture

In addition, properly designing self-service password reset requires the admin to create security

questions that users will answer. Ideally, admins should create groups of questions around

different categories then require users to answer a subset of questions for each group. The

questions must be something the user knows that does not change and is not known by others.

User Profiles

A user’s profile plays a critical role in delivering a consistently positive experience within a virtual

desktop or virtual application scenario. Even a well-designed virtual desktop solution can fail if users

are frustrated due to lengthy logon times or lost settings.

The user profile solution chosen must align with the personalization characteristics of the user

group captured during the assess phase as well as the VDI model selected.

Decision: Profile Type

This section provides an overview on the different profile types available and provides guidance

on the optimal user profile for each VDI model.

 Local profiles – Local profiles are stored on each server or desktop operating system and

are initially created based on the default user profile. Therefore, a user accessing these

resources would create an independent profile on each system. Users are able to retain

changes to their local profile on each individual system, but changes are only accessible

for future sessions on that system. Local profiles require no configuration; if a user

logging into a server or desktop operating system does not have a profile path

administratively defined, a local profile is created by default.

 Roaming profiles – Roaming profiles are stored in a centralized network repository for

each user. Roaming profiles differ from local profiles in that the information in the

profile (whether it is a printer, a registry setting, or a file stored in the documents folder)

can be made available to user sessions accessed from all systems in the environment.

Configuring a user for a roaming profile requires an administrator to designate the

user’s profile path (for virtual desktops) or terminal server profile path to a particular

network share. The first time the user logs on to a server or desktop operating system,

the default user profile is used to create the user’s roaming profile. During logoff, the

profile is copied to the administrator-specified network location.

 Mandatory profiles – Mandatory profiles are typically stored in a central location for

many users. However, the user’s changes are not retained at logoff. Configuring a user

for a mandatory profile requires an administrator to create a mandatory profile file

(NTUSER.MAN) from an existing roaming or local profile and assign users with a terminal

services profile path. This can be achieved by means of Microsoft Group Policy,

customizing the user properties in Active Directory or Citrix Profile Management.

User StoreFront SSPR Service

Active Directory

Central Store

TLS

LDAP

SMB

TLS

Self Service Account

Data Proxy Account

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 Hybrid profiles – Hybrid profiles combine a robust profile core (a mandatory profile or a

local default profile) with user specific registry keys or files that are merged during logon.

This technique enables administrators to tightly control which changes are retained and

to keep the user profiles small in size. Furthermore, hybrid profiles address the last write

wins issue using mature queuing techniques that automatically detect and prevent

simultaneous writes that could potentially overwrite changes made in another session.

Thus minimizing user frustration resulting from lost profile changes when accessing

multiple servers or virtual desktops simultaneously. In addition, they capture and record

only the changes within the profile, rather than writing the entire profile at logoff. A

good example of a hybrid profile solution is Citrix Profile Management, which will be

discussed in detail within this chapter.

The following table compares the capabilities of each profile type:

Feature

Local

Roaming

Mandatory

Hybrid

Central management

/ roams with user





User settings are

stored persistently







Granular capture of

user settings





“”: Functionality available “º”: Optional ““: Functionality not available

Table 22: Profile Type Capability Comparison

In order to select the optimal profile type for each user group it is important to understand their

personalization requirements in addition to the VDI model assigned.

The following table provides recommendations on selecting the appropriate user profile type

based on VDI resource:

Local

Roaming

Mandatory

Hybrid

User setting persistence required (personalization characteristic: basic / complete)

Hosted Windows App









Hosted Browser App









Hosted Shared Desktop









Hosted Pooled Desktop









Hosted Personal Desktop







Hosted Pro Graphics Desktop







Local Streamed Desktop









Local VM Desktop





Remote PC Access





User setting persistence not required or not desired (personalization characteristic: none)

Hosted Windows App







Hosted Browser App







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Hosted Shared Desktop







Hosted Pooled Desktop









Hosted Personal Desktop







Hosted Pro Graphics Desktop







Local Streamed Desktop









Local VM Desktop







Remote PC Access







“”: Recommended “º”: Viable ““: Not Recommended

Table 23: Profile Type Selection

Decision: Folder Redirection

Redirecting special folders can supplement any of the described profile types. While redirecting

profile folders, such as user documents and favorites, to a network share is a good practice to

minimize profile size, architects need to be aware that applications may frequently read and

write data to profile folders such as AppData, causing potential issues with file server utilization

and responsiveness. It is important to thoroughly test profile redirection before implementation

in production to avoid these issues. Therefore, it is important to research profile read / write

activities and to perform a pilot before moving to production. Microsoft Outlook is an example

of an application that regularly performs profile read activities, as the user signature is read from

the user profile every time an email is created.

The following table provides general recommendations to help identify the appropriate folders

to redirect:

Folder

Local

Roaming

Mandatory

Hybrid

Application Data



Contacts







Desktop







Downloads



Favorites



Links







My Documents



My Music



My Pictures



My Videos



Saved Games



Searches







Start Menu



“”: Recommended “º”: Optional ““: Not recommended

Table 24: Folder Redirection Matrix

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Decision: Folder Exclusion

Excluding folders from being persistently stored as part of a roaming or hybrid profile can help to

reduce profile size and logon times. By default Windows excludes the AppData\Local and

AppData\LocalLow folders, including all subfolders, such as History, Temp and Temporary

Internet Files. In addition, the downloads and saved games folders should also be excluded. All

folders that are redirected should be excluded from the profile solution.

Decision: Profile Caching

Local caching of roaming or hybrid user profiles on a server or virtual desktop is default Windows

behavior and can reduce login times and file server utilization / network traffic. With profile

caching, the system only has to download changes made to the profile. The downside of profile

caching is that it can consume significant amounts of local disk storage on multi-user systems,

such as a hosted shared desktop hosts.

In certain VDI models and configurations, the VDI resource is reset to a pristine state. Having

locally cached profiles be deleted upon logoff is an unnecessary consumption of resources.

Based on this, the leading recommendation is to not deleting locally cached profiles for the

following VDI models:

 Hosted Personal Desktops

 Hosted Pooled Desktops – only in situations where a reboot occurs after logoff.

 Local VM Desktops

 Remote PC Access

Configuring the “Delay before deleting cached profiles” Citrix policy sets an optional extension to

the delay before locally cached profiles are deleted at logoff. Extending the delay is useful if a

process keeps files or the user registry hive open during logoff. This can also reduce logoff times

for large profiles.

Decision: Profile Permissions

For security reasons, administrators, by default, cannot access user profiles. While this level of

security may be required for organizations that deal with very sensitive data, it is unnecessary for

most environments and can complicate operations and maintenance. Therefore, consider

enabling the “Add the Administrators security group to roaming user profiles” policy setting. The

configuration of this policy should be aligned with the security characteristics of the user groups

captured during the assess phase. For more information on the permissions required for the file

share hosting user profiles and data, please refer to Microsoft TechNet - Deploying Roaming

Profiles.

Decision: Profile Path

Determining the network path for the user profiles is one of the most significant decisions

during a user profile design process. In general, it is strongly recommended to leverage a

redundant and high performance file server or NAS device.

There are four topics that must be considered for the profile share:

 Performance – File server performance will affect logon and logoff times, and

depending on other decisions such as redirected folders and profile streaming, can

impact the user’s experience within the session. For large virtual desktop infrastructures,

a single file server cluster may not be sufficient to handle periods of peak activity. In

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order to distribute the load across multiple file servers, the file server address and share

name will need to be adjusted.

 Location – User profiles are transferred over the network by means of the SMB protocol,

which does not perform well on high-latency network connections. Furthermore, WAN

connections are typically bandwidth constrained, which can add additional delay to the

profile load process. Therefore, the file server should be located in close proximity to the

servers and virtual desktops to minimize logon times.

 Operating system platforms – User profiles have a tight integration with the underlying

operating system and it is not supported to reuse a single user profile on different

operating systems or different platforms like 64-Bit (x64) and 32-Bit (x86). For more

information, please refer to the Microsoft knowledge base article KB2384951 – Sharing

32 and 64-bit User Profiles. Windows 2008 and Windows Vista introduced a new user

profile structure, which can be identified by .V2 profile directory suffix, which makes

older user profiles incompatible with newer operating systems such as Windows 2012, 7

and 8. In order to ensure that a separate profile is used per platform, the profile directory

has to be adapted.

 Indexing capabilities – To take full advantage of Windows Search functionality on a

user’s redirected data, Windows file servers that index the user’s data must be used, as

opposed to a share on a NAS appliance. This is important for use cases that are heavily

dependent on Windows Search or are especially sensitive to perception of slowness or

latency.

There are two methods that can be used to address these challenges that are based on

Windows built-in technology:

 User object – For every user object in Active Directory, an individual profile path, which

contains file server name and profile directory, can be specified. Since only a single

profile path can be specified per user object, it is not possible to ensure that a separate

profile is loaded for each operating system platform.

 Computer group policy or system variables – The user profile path can also be

configured by means of computer specific group policies or system variables. This

enables administrators to ensure that a user profile is dedicated to the platform. Since

computer specific configurations affect all users of a system, all user profiles will be

written to the same file server. To load balance user profiles across multiple servers

dedicated XenDesktop delivery groups have to be created per file server.

Note: Microsoft does not support DFS-N combined with DFS-R for actively used user profiles. For

more information, please refer to the Microsoft articles:

 Information about Microsoft support policy for a DFS-R and DFS-N deployment scenario

 Microsoft’s Support Statement Around Replicated User Profile Data

When using Citrix Profile Management, a third option is available to address these challenges:

User object attributes and variables – Citrix Profile Management enables the administrator to

configure the profile path by means of a computer group policy using attributes of the user

object in Active Directory to specify the file server dynamically. In order to achieve this, three

steps are required:

1. Create a DNS alias (for example, fileserver1) that refers to the actual file server

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2. Populate an empty LDAP attribute of the user object (for example, l or UID) with the DNS

Alias

3. Configure Citrix Profile Management by means of GPO to use a profile path that refers

to the LDAP attribute (for example, if attribute UID is used the profile path becomes

\\#UlD#\Profiles\profiledirectory)

In addition, Citrix Profile Management automatically populates variables to specify the profile

path dynamically based on the operating system platform. Valid profile management variables

are:

 !CTX_PROFILEVER! – Expands to v1 or v2 depending on the profile version.

 !CTX_OSBITNESS! – Expands to x86 or x64 depending on the bit-level of the operating

system.

 !CTX_OSNAME! – Expands to the short name of the operating system, for example Win7

By combining both capabilities of Citrix Profile Management, a fully dynamic user profile path

can be created, which can be load balanced across multiple file servers and ensure profiles of

different operating system platforms are not mixed. An example of a fully dynamic user profile

path is shown below:

\\#UID#\profiles$\%USERNAME%.%USERDOMAIN%\!CTX_OSNAME!!CTX_OSBITNESS!

Decision: Profile Streaming

Note: The following design decision only applies to those environments that use Citrix Profile

Management.

With user profile streaming, files and folders contained in a profile are fetched from the user

store (file server) to the local computer when a user accesses them. During the logon process,

Citrix Profile Management immediately reports that the profile load process has completed

reducing profile load time to almost zero.

Citrix recommends enabling profile streaming for all scenarios. If it is desired to keep a local

cached copy of the user profile for performance reasons, it is recommended to enable the

“Always Cache” setting and configure a size of 0. This ensures that the user profile is downloaded

in the background and enables the system to use this cached copy going forward.

Decision: Active Write Back

Note: The following design decision only applies to those environments that use Citrix Profile

Management.

By enabling the active write back feature, Citrix Profile Manager detects when an application has

written and closed a file and copies the file back to the network copy of the profile during idle

periods. In scenarios where a single user leverages multiple virtual desktops or hosted shared

desktops simultaneously, this feature can be tremendously beneficial. However, Citrix Profile

Management does not copy any registry changes back to the network, except during an ordered

logoff. As such, there is a risk that the registry and files may get out of alignment on non-

Experience from the Field

General – Some poorly written applications might load faster if their AppData has already been

streamed to the VDI resource. Enabling the “Always Cache” option for profile streaming can help

improve performance when the AppData folder is not redirected.

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persistent systems, where locally cached profile information is wiped upon reboot. Therefore, it is

recommended to disable active write back functionality for non-persistent scenarios.

Decision: Configuration Approach

Note: The following design decision only applies to those environments that use Citrix Profile

Management.

Citrix Profile Management can be configured by means of an “.ini” file, Microsoft Group Policy

and Citrix Policy (Citrix Profile Management 5.0 and newer). While each option offers the same

configuration settings, Group Policy is recommended because it allows administrators to

perform Windows and Citrix profile configurations from a single point, minimizing the tools

necessary for profile management.

Note: With Citrix Profile Management 5.0 and newer, the desktop type is automatically detected

and Citrix Profile Management policies set accordingly. For more information, please refer to Citrix

Docs – How automatic configuration works.

Decision: Replication

While having an active/active datacenter on a network level is easily accomplished with GSLB,

the replication of user data makes having a fully active/active deployment complex in most

situations. To have an active/active configuration where users are not statically assigned to a

specific datacenter, will require users to have no form of personalization requirements. This will

limit the user’s ability to make any configuration changes and will not allow them to create any

documents or persistent data. The exception to this is when a high-speed, low latency

connection such as dark fiber is available between datacenters. This will let resources in both

locations can point to the same file server allowing for a true active/active solution. Also, an

active/active configuration can be accomplished when applications are used that rely solely on a

backend database that is actively replicated between datacenters and do not store any data in

the user profile.

For redundancy and failover purposes, user data such as Windows profiles and documents

should be synchronized between datacenters. Although it is recommended to replicate user

data between datacenters, the replication would be an active/passive configuration. This means

the data can only be actively consumed from a single datacenter. The reason for this limitation is

the distributed file locking method inside Windows that only allows a single user to actively write

to a file. Therefore, active/active replication of user data is not supported. Any supported

configuration consists of a one-way replication of data that is active in a single datacenter at any

point in time.

For example, the figure below describes a scenario where user data is passively replicated from

Datacenter A to Datacenter B. In this example, File Server A is the primary location for user data

in Datacenter A and File Server B is the primary location in Datacenter B. One-way replication of

the user data occurs for each fileserver to allow for the user data to be available in the opposite

datacenter if a failover occurs. Replication technologies such as Microsoft DFS can be configured

to mirror user profiles and documents to a file server in another datacenter. DFS Namespaces

can also be used to have a seamless path for the location of the user data. However,

implementing a replication solution like this requires an administrator familiar with Microsoft

DFS and user profiles.

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User Data

In order to be effective, users must access their data. The data must be in close proximity to the

application for the user to have a good experience. As the distance between the application and

data increases, latency also increases, which slows down any file operation (opening, saving,

modifying).

In a VDI-based environment, administrators must understand where users store their data and

impact of access.

Decision: User Data Location

Users traditionally stored their data on their local device or on a network file server designated

with a drive mapping. Due to IT storage space limitations or the inability to have the data follow

the user to other mobile devices, users turned to free, cloud-based storage offerings like

OneDrive, DropBox and Box. To get access to the data, the user would install the storage

vendor’s agent on their traditional Windows PC, allowing them direct access to the cloud-hosted

storage repository.

Administrators must design the solution to take into account user storage by looking at the

following options:

 Multi-Agent Strategy – In VDI, users require the admin to install and configure the agent

for each storage provider, which assumes the storage agent supports the non-persistent

VDI model. Each agent is a new application that the admin must manage and maintain.

 Storage Connector Strategy – A single agent consolidates storage repositories from

numerous cloud-hosted and on-premises providers into a single folder structure. For

Datacenter B

Datacenter A

Primary Mirror

File Server A

File Server B

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example, when a user connects to Citrix ShareFile, they see a consolidated folder

structure containing their user data from the cloud (ShareFile, OneDrive, DropBox, Box

and Google Drive) and from on-premises (SharePoint, Windows network shares and

local endpoint shares).

Decision: User Data Access

A critical aspect to a successful VDI solution is for the user experience to remain the same as it

was with a traditional PC. If users open files from within the application, that functionality must

continue to function. If users navigate with Explorer to access a file, that functionality must

continue to function.

A user’s data can exist on the local PC, on a network file share and hosted in the cloud.

Figure 25: User Data Storage Locations

With local PC, on-premises network shares and cloud-hosted storage options available to users,

administrators need to understand how users accessing their data affects the infrastructure and

VDI experience.

 Direct Data Access – Users access a file on a remote server (on-premises Windows server

or cloud-hosted storage provider). The distance between the application and file directly

affects the experience. Longer distances equates to higher latency. Each file operation

(navigate, open, close, save, etc.) takes more time as the latency between application and

file storage increases. Windows file servers are often located in the same data center as

the user’s VDI desktop making direct data access feasible; but cloud-hosted solutions

and local PC Access will experience poor response times if the connection between the

VDI desktop and the storage repository has high latency.

 Local Synchronization – With a traditional PC, users are accustomed to having files local,

which mitigates any slow application response times due to extremely low latency. Many

cloud-hosted solutions provide data synchronization to enable access speeds similar to

a local storage model. Many of the cloud-hosted solutions provide full synchronization

or user-configured partial synchronization of certain folders and files. With partial

synchronization, only the synchronized files are visible and accessible on the device,

causing user confusion. Full and partial synchronization increases VDI costs. Each session

is an entirely new desktop requiring synchronization of user’s folders/files, which takes

time, network bandwidth and VDI storage space. Every file synchronized to the VDI

User

Virtual Desktop/App

Cloud-Hosted Storage

Windows File Share

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desktop must be stored within the organization’s data center for the duration of the VDI

session.

 On-Demand Synchronization – When navigating Explorer, users see a complete, but

virtual, file/folder structure even though those files/folders do not physically exist on the

desktop. Selecting a file begins an automatic synchronization to the VDI desktop for that

single file. At this point, file access is local, which creates a user experience like that of a

traditional PC. When the user saves or closes the file, the file synchronizes back to the

cloud. Only the files accessed synchronize, eliminating the waste incurred with the local

data access model. Citrix ShareFile includes Drive Mapper, allowing the user to interact

with their data via Explorer while utilizing on-demand synchronization when accessing a

file. As only accessed files synchronize, the impact to the underlying storage

infrastructure and associated storage costs are minimal.

Direct Data Access

Local

Synchronization

On-Demand

Synchronization

Network File Server



Cloud-hosted





Local PC





“”: Recommended ““: Not recommended

Table 25: User Data Access Recommendations for VDI

Decision: Data Recovery

File corruption is an issue most users experience. Improperly shutting down the application or PC

(hitting the power button instead of closing the application and shutting down the operating

system gracefully) often causes many corruption issues.

A few options exist to provide users with data recovery options:

 Multi-File – With a traditional PC, users have few recovery options if the files are local.

Users often manually create a new copy of the file each day in order to provide some

level of recovery. This solution is hard to manage.

 Backup/Restore – Administrators can implement a backup and restore solution to help

with file recovery. However, these solutions rarely work with local files and for a network

file share, the backup process usually only runs nightly or weekly. In addition, restoring a

corrupted file requires the user to call support.

 Versioning –Cloud-hosted options, like Citrix ShareFile, include file versioning, which

automatically creates new versions of the file as changes are saved. Versioning requires

no user intervention and allows users to recover from corruption quickly and with little

loss of data.

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Figure 26: ShareFile Versioning

Policies

Policies provide the basis to configure and fine tune XenApp and XenDesktop environments,

allowing organizations to control connection, security and bandwidth settings based on various

combinations of users, devices or connection types.

When making policy decisions it is important to consider both Microsoft and Citrix policies to ensure

that all user experience, security and optimization settings are considered. For a list of all Citrix-

related policies, please refer to the Citrix Policy Settings Reference.

Decision: Preferred Policy Engine

Organizations have the option to configure Citrix policies via Citrix Studio or through Active

Directory group policy using Citrix ADMX files, which extend group policy and provide advanced

filtering mechanisms.

Using Active Directory group policy allows organizations to manage both Windows policies and

Citrix policies in the same location, and minimizes the administrative tools required for policy

management. Group policies are automatically replicated across domain controllers, protecting

the information and simplifying policy application.

Citrix administrative consoles should be used if Citrix administrators do not have access to Active

Directory policies. Architects should select one of the above two methods as appropriate for

their organization’s needs and use that method consistently to avoid confusion with multiple

Citrix policy locations.

It is important to understand how the aggregation of policies, known as policy precedence flows

in order to understand how a resultant set of policies is created. With Active Directory and Citrix

policies, the precedence is as follows:

Policy Precedence

Policy Type

Processed first (lowest

precedence)

Local server policies

Processed second

Citrix policies created using the Citrix

administrative consoles

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Processed third

Site level AD policies

Processed fourth

Domain level AD policies

Processed fifth

Highest level OU in domain

Processed sixth and

subsequent

Next level OU in domain

Processed last (highest

precedence)

Lowest level OU containing object

Table 26: Policy Precedence

Policies from each level are aggregated into a final policy that is applied to the user or computer.

In most enterprise deployments, Citrix administrators do not have rights to change policies

outside their specific OUs, which will typically be the highest level for precedence. In cases where

exceptions are required, the application of policy settings from higher up the OU tree can be

managed using “block inheritance” and “no override” settings. Block inheritance stops settings

from higher-level OUs (lower precedence) from being incorporated into the policy. However, if a

higher-level OU policy is configured with no override, the block inheritance setting will not be

applied. Given this, care must be taken in policy planning, and available tools such as the “Active

Directory Resultant Set of Policy” tool or the “Citrix Group Policy Modeling” wizard should be

used to validate the observed outcomes with the expected outcomes.

Note: some Citrix policy settings, if used, need to be configured through Active Directory group

policy, such as Controllers and Controller registration port, as these settings are required for VDAs

to register.

Decision: Policy Integration

When configuring policies, organizations often require both Active Directory policies and Citrix

policies to create a completely configured environment. With the use of both policy sets, the

resultant set of policies can become confusing to determine. In some cases, particularly with

respect to Windows Remote Desktop Services (RDS) and Citrix policies, similar functionality can

be configured in two different locations. For example, it is possible to enable client drive

mapping in a Citrix policy and disable client drive mapping in a RDS policy. The ability to use the

desired feature may be dependent upon the combination of RDS and Citrix policy. It is important

to understand that Citrix policies build upon functionality available in Remote Desktop Services.

If the required feature is explicitly disabled in RDS policy, Citrix policy will not be able to affect a

configuration as the underlying functionality has been disabled.

In order to avoid this confusion, it is recommended that RDS policies only be configured where

required and there is no corresponding policy in the XenApp and XenDesktop configuration, or

the configuration is specifically needed for RDS use within the organization. Configuring policies

at the highest common denominator will simplify the process of understanding resultant set of

policies and troubleshooting policy configurations.

Decision: Policy Scope

Once policies have been created, they need to be applied to groups of users and/or computers

based on the required outcome. Policy filtering provides the ability to apply policies against the

requisite user or computer groups. With Active Directory based policies, a key decision is whether

to apply a policy to computers or users within site, domain or organizational unit (OU) objects.

Active Directory policies are broken down into user configuration and computer configuration.

By default, the settings within the user configuration apply to users who reside within the OU at

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logon, and settings within the computer configuration are applied to the computer at system

startup, and will affect all users who logon to the system. One challenge of policy association

with Active Directory and Citrix deployments revolves around three core areas:

 Citrix environment specific computer policies – Citrix servers and virtual desktops often

have computer policies that are created and deployed specifically for the environment.

Applying these policies is easily accomplished by creating separate OU structures for the

servers and the virtual desktops. Specific policies can then be created and confidently

applied to only the computers within the OU and below and nothing else. Based upon

requirements, virtual desktops and servers may be further subdivided within the OU

structure based on server roles, geographical locations or business units.

 Citrix specific user policies – When creating policies for XenApp and XenDesktop there

are a number of policies specific to user experience and security that are applied based

on the user’s connection. However, the user’s account could be located anywhere within

the Active Directory structure, creating difficulty with simply applying user configuration

based policies. It is not desirable to apply the Citrix specific configurations at the domain

level as the settings would be applied to every system any user logs on to. Simply

applying the user configuration settings at the OU where the Citrix servers or virtual

desktops are located will also not work, as the user accounts are not located within that

OU. The solution is to apply a loopback policy, which is a computer configuration policy

that forces the computer to apply the assigned user configuration policy of the OU to

any user who logs onto the server or virtual desktop, regardless of the user’s location

within Active Directory. Loopback processing can be applied with either merge or

replace settings. Using replace overwrites the entire user GPO with the policy from the

Citrix server or virtual desktop OU. Merge will combine the user GPO with the GPO from

the Citrix server or desktop OU. As the computer GPOs are processed after the user

GPOs when merge is used, the Citrix related OU settings will have precedence and be

applied in the event of a conflict. For more information, please refer to the Microsoft

TechNet article - Understand User Group Policy Loopback Mode.

 Active Directory policy filtering – In more advanced cases, there may be a need to apply a

policy setting to a small subset of users such as Citrix administrators. In this case,

loopback processing will not work, as the policy should only be applied to a subset of

users, not all users who logon to the system. Active Directory policy filtering can be used

to specify specific users or groups of users to which the policy is applied. A policy can be

created for a specific function, and then a policy filter can be set to apply that policy only

to a group of users such as Citrix administrators. Policy filtering is accomplished using

the security properties of each target policy.

Citrix policies created using Citrix Studio have specific filter settings available, which may be used

to address policy-filtering situations that cannot be handled using group policy. Citrix policies

may be applied using any combination of the following filters:

Filter Name

Filter Description

Scope

Access control

Applies a policy based on access control

conditions through which a client is connecting.

For example, users connecting through a Citrix

NetScaler Gateway can have specific policies

applied.

User settings

Citrix CloudBridge

Applies a policy based on whether or not a user

session was launched through Citrix CloudBridge.

User settings

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Client IP address

Applies a policy based on the IPv4 or IPv6 address

of the user device used to connect the session.

Care must be taken with this filter if IPv4 address

ranges are used in order to avoid unexpected

results.

User settings

Client name

Applies a policy based on the name of the user

device used to connect the session.

User settings

Delivery group

Applies a policy based on the delivery group

membership of the desktop running the session

User and computer settings

Delivery group

type

Applies a policy based on the type of machine

running the session. For example, different

policies can be set depending upon whether a

desktop is pooled, dedicated or streamed.

User and computer settings

Organizational

unit

Applies a policy based on the OU of the desktop

or server running the session.

User and computer settings

Tag

Applies a policy based on any tags applying to

the desktop running the session. Tags are strings

that can be added to virtual desktops in

XenDesktop environments that can be used to

search for or limit access to desktops.

User and computer settings

User or group

Applies a policy based on the Active Directory

group membership of the user connecting to the

session.

User settings

Table 27: Citrix Policy Filters

Note: Citrix policies in XenDesktop 7.x provide a merged view of settings that apply at the user

and computer level. In table 24, the Scope column identifies whether the specified filter applies to

user settings, computer settings, or both.

Decision: Baseline Policy

A baseline policy should contain all common elements required to deliver a high-definition

experience to the majority of users within the organization. A baseline policy creates the

foundation for user access, and any exceptions that may need to be created to address specific

access requirements for groups of users. It should be comprehensive to cover as many use cases

as possible and should have the lowest priority, for example 99 (a priority number of “1” is the

highest priority), in order to create the simplest policy structure possible and avoid difficulties in

determining the resultant set of policies. The unfiltered policy set provided by Citrix as the default

policy may be used to create the baseline policy as it is applied to all users and connections. In

the baseline configuration, all Citrix policy settings should be enabled, even those that will be

configured with the default value, in order to explicitly define desired/expected behavior, and to

avoid confusion should default settings change over time.

Citrix Policy templates can be used to configure Citrix policies to effectively manage the end-user

experience within an environment and can serve as an initial starting point for a baseline policy.

Templates consist of pre-configured settings that optimize performance for specific

environments or network conditions. The built-in templates included in XenDesktop are shown

below:

Built-in Templates

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High definition user

experience

Includes settings for providing high quality audio,

graphics, and video to users.

High server scalability

Includes settings for providing an optimized user

experience while hosting more users on a single

server.

Optimized bandwidth for

WAN

Includes settings for providing an optimized

experience to users with low bandwidth or high

latency connections.

Security and control

Includes settings for disabling access to peripheral

devices, drive mapping, port redirection, and Flash

acceleration on user devices.

Table 28: XenDesktop 7 Built-in Policy Templates

For more information on Citrix policy templates, please refer to Citrix Docs - Manage Citrix Policy

Templates.

A baseline policy configuration should also include Windows policies. Windows policies reflect

user specific settings that optimize the user experience and remove features that are not

required or desired in a XenDesktop environment. For example, one common feature turned off

in these environments is Windows update. In virtualized environments, particularly where

desktops and servers may be streamed and non-persistent, Windows update creates processing

and network overhead, and changes made by the update process will not persist a restart of the

virtual desktop or application server. Also in many cases, organizations use Windows software

update service (WSUS) to control Windows updates. In these cases, updates are applied to the

master disk and made available by the IT department on a scheduled basis.

In addition to the above considerations, an organization’s final baseline policy may include

settings specifically created to address security requirements, common network conditions, or to

manage user device or user profile requirements:

Printing

Citrix XenApp and Citrix XenDesktop support a variety of different printing solutions. In order to plan

and successfully implement the proper printing solution it is important to understand the available

technologies as well as their benefits and limitations.

Decision: Printer Provisioning

The process of creating printers at the start of a XenApp or XenDesktop session is called printer

provisioning. There are multiple approaches available:

 User Added – Allowing users to manually add printers gives them the flexibility to select

printers by convenience. The drawback to manually adding network-based printers is

that it requires the users to know the network name or path of the printers. There is also

a chance that the native print driver is not installed in the operating system and the Citrix

Universal Print Driver is not compatible, thereby requiring the user to seek administrative

assistance. Manually adding printers is best suited in the following situations:

o Users roam between different locations using the same client device (i.e. laptop,

tablet).

o Users work at assigned stations or areas whose printer assignments will rarely

change.

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o Users have personal desktops with sufficient rights to install necessary printer

drivers.

 Auto Created – Auto-creation is a form of dynamic provisioning that attempts to create

some or all of the available printers on the client device at the start of a user session. This

includes locally attached printers as well as network-based printers. Auto-creating all

client printers can increase the session logon time as each printer is enumerated during

the logon process.

 Session Based – Session printers are a set of network-based printers assigned to users

through a Citrix policy at the start of each session.

o Proximity based session printers are filtered by IP subnet. The network printers

created under this policy may vary based on where the user’s endpoint device is

located. Proximity printing is recommended in situations where: Users roam

between different locations using the same endpoint device (i.e. laptop, tablet)

and where thin clients are used, which do not have the ability to connect to

network-based printers directly.

o Session printers may be assigned using the “Session Printer” policy or the

“Printer Assignments” policy. The “Session printer” policy is intended to be used

to set default printers for a farm, site, large group, or OU. The “Printer

Assignments” policy is used to assign a large group of printers to multiple users.

If both policies are enabled and configured, the session printers will be merged

into a single list.

 Universal Printer – The Citrix Universal Printer is a generic printer object that is auto-

created at the start of a session and is not linked to a printing device. When using the

Citrix Universal Printer, it is not required to enumerate the available client printers during

logon, which can greatly reduce resource usage and decrease user logon times. By

default, the Citrix Universal Printer will print to the client’s default printer, however the

behavior can be modified to allow the user to select any of their compatible local or

network-based printers.

The Citrix Universal Printer is best suited for the following scenarios:

 The user requires access to multiple printers both local and network-based which

may vary with each session.

 The user’s logon performance is a priority and the Citrix policy “Wait for printers to

be created” must be enabled due to application compatibility.

 The user is working from a Windows based device or thin client.

Note: Other options for provisioning printers, such as Active Directory group policy, “follow-me”

centralized print queue solutions, and other 3

party print management solutions can be used to

provision printers into a Citrix session.

Decision: Printer Drivers

Managing print drivers in XenApp and XenDesktop can be a tedious task, especially in large

environments with hundreds of printers. In XenApp and XenDesktop there are several methods

available to assist with print driver management.

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 User Installed – When adding a printer within a XenApp or XenDesktop session and the

native print driver is not available, the drivers can be installed manually, by the user. Many

different print drivers can potentially be installed on different resources creating

inconsistencies within the environment. Troubleshooting printing problems and

maintenance of print drivers can become very challenging since every hosted resource

may have different sets of print drivers installed. To ensure consistency and simplify

support and troubleshooting, user installed drivers is not recommended.

 Automatic Installation – When connecting a printer within a XenApp or XenDesktop

session, a check is made to see if the required print driver is already installed in the

operating system. If the print driver is not already installed, the native print driver, if one

exists, will be installed automatically. If users roam between multiple endpoints and

locations, this can create inconsistencies across sessions since users may access a

different hosted resource every time they connect. When this type of scenario occurs,

troubleshooting printing problems and maintenance of print drivers can become very

challenging since every hosted resource may have different sets of print drivers installed.

To ensure consistency and simplify support and troubleshooting, automatic installed

drivers is not recommended.

 Universal Print Driver – The Citrix Universal Printer Driver (UPD) is a device independent

print driver, which has been designed to work with most printers. The Citrix Universal

Printer Driver (UPD) simplifies administration by reducing the number of drivers required

on the master image. For auto created client printers, the driver records the output of

the application and sends it, without any modification, to the end-point device. The

endpoint uses local, device-specific drivers to finish printing the job to the printer. The

UPD can be used in conjunction with the Citrix Universal Print Server (UPServer) to

extend this functionality to network printers.

Decision: Printer Routing

Print jobs can be routed along different paths: through a client device or through a print server.

 Client Device Routing – Client devices with locally attached printers (printers attached

through USB, LPT, COM, TCP, etc.) will route print jobs directly from the client device to

the printer.

 Windows Print Server Routing – By default, print jobs sent to auto-created network-

based printers will be routed from the user’s session to the print server. However, the

print job will take a fallback route through the client device when any of the following

conditions are true:

o The session cannot contact the print server

o The print server is on a different domain without a trust established

o The native print driver is not available within the user’s session

 Citrix Universal Print Server Routing – Print job routing follows the same process as

Windows Print Server Routing except that the Universal Print Driver is used between the

user’s session and the Citrix Universal Print Server.

The specifics with print job routing are based on the printer provisioning method. Auto-created

and user-added printers can route print jobs based on the following diagrams:

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Figure 27: Auto-created and User-Added Print Job Routing

However, if the printers are provisioned as session printers, the print job routing options changes

slightly. The jobs are no longer able to route through the user’s endpoint device.

Figure 28: Session Printers Print Job Routing

The recommended option is based on the network location of the endpoint device, the user’s

session and the print server.

 Client Device Routing

Locally

Attached Printer

Endpoint

Session

HDX

Compressed Print Job

Print Job

Client Device Routing

Network

Attached Printer

Endpoint

Session

HDX

Print Job (fallback)

Print Job

Windows Print Server Routing

Print Server

Print Job

Network

Attached Printer

Endpoint

Session

HDX

Print Job (fallback)

Compressed

Print Job

Windows Print Server Routing (with Universal Print Server)

Universal

Print Server

Network

Attached Printer

Endpoint

Session

HDX

Print Job

Windows Print Server Routing

Windows

Print Server

Print Job

Network

Attached Printer

Endpoint

Session

HDX

Compressed

Print Job

Citrix Universal Print Server Routing

Universal

Print Server

Print Job

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o Use for locally attached printer implementations.

o Use if a Windows endpoint device and printer are on the same high-speed, low-

latency network as the Windows Print Server.

 Windows Print Server Routing

o Use if the printer is on the same high-speed, low-latency network as the

Windows Print Server and user session.

 Windows Print Server Routing (with Universal Print Server)

o Use if non-Windows endpoint device and printer are on the same high-speed,

low-latency network as the Windows Print Server.

Decision: Print Server Redundancy

Network-based printers, managed with a Microsoft print server or the Citrix Universal Print Server

should be configured with redundancy in order to eliminate a single point of failure. The Citrix

Universal Print Server redundancy should be defined within a Citrix Policy.

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Applications

Properly integrating an application requires understanding compatibility and how the user/business

requirements influences the appropriate delivery method.

Decision: Compatibility

VDI typically requires significant changes to be made to an organization’s application delivery

and management strategy. For example, many organizations will take the opportunity to

upgrade their desktop operating system and to simplify management by reducing the number

of applications installed into the base image using techniques such as application streaming and

application layering. These are significant changes that require comprehensive compatibility

testing. Important compatibility requirements that may need to be verified include:

 Operating system –the application must be compatible with the preferred operating

system.

 Multi-User – Some applications may be more appropriate for delivery via a hosted

shared desktop or a hosted Windows App. In these situations, the compatibility of the

Experience from the Field

A print media company leverages Thin Clients and Windows-based workstations at the company

headquarters. Network based printers are placed throughout the building (one per floor). Windows

print servers reside in the datacenter and manage the network printers. XenDesktop and XenApp

servers also reside in the datacenter.

A regional office has numerous Windows, Linux and Mac endpoints with network attached printers.

A remote branch office has a few Windows workstations with locally attached printers.

Three different print strategies are applied:

Headquarters

A Citrix Universal Print Server is used for printing within the XenApp and XenDesktop session. Native

print drivers are not required on the Windows based workstations. A session printer policy is configured

per floor which connects the floor printer as the default printer. The policies are filtered based on the

subnet of the thin client for proximity printing.

Quality of Service (QoS) policies are implemented. Inbound and outbound network traffic on ports TCP

1494 and TCP 2598 are prioritized over all other network traffic. This will prevent HDX user sessions

from being impacted by large print jobs.

Regional Office

A Universal Print Server is deployed within the regional office. The print job uses the Universal Print

Driver and is compressed and delivered from the user’s session to the Universal Print Server, across the

WAN. The job is then sent to the network-attached printer in the office.

Branch Office

Since all branch users work on Windows based workstations, auto-created client printers in

conjunction with the Citrix Universal Printer Driver are used. Since the print job is delivered over ICA, the

print data is compressed which saves bandwidth. The Citrix Universal Printer Driver ensures all printers

connected to the client can be used within the XenApp or XenDesktop session without concern of the

printer model used.

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application must be verified against the multi-user capabilities of a server operating

system like Windows Server 2012R2.

 Application architecture – It is important to understand whether the application includes

16-bit, 32-bit or 64-bit code so that an appropriate operating system can be selected.

16-bit code cannot be executed on a 64-bit operating system. However, a 16-bit

application can be delivered to users as a Hosted Windows App from a 32-bit desktop-

based operating system like x86 editions of Windows 7, 8 or 10.

 Interoperability – Some applications may experience complications if they coexist on the

same operating system. Possible causes include shared registry hives, dll files or INI files

as well as incompatible dependencies. Application interoperability issues should be

identified so that appropriate remediation steps can be taken or an alternative delivery

model selected.

 Dependency – Applications may need to interact with each other to provide the users

with a seamless experience. For example, applications that present information in a PDF

format require a suitable PDF viewer to be available. Many times, the dependent (child)

applications are version specific to the parent application.

 Application virtualization – The use of application virtualization techniques, like

streaming and layering, helps to simplify image management by reducing the number of

applications installed into the base image. However, not all applications are suitable for

streaming and layering because they may install device drivers, use COM+ or form part

of the operating system.

Application compatibility can be achieved by doing a combination of manual, user testing,

utilizing pre-verified lists maintained by the software vendor, or using an automated application

compatibility solution, like Citrix AppDNA, which runs through thousands of tests to verify

compatibility.

Decision: Application Delivery Method

It is unlikely that a single delivery method will meet all requirements. Based on the outcome of

the application categorization assessment process and the overall image management strategy

(installed images, scripted images and layered images), several application delivery methods can

be considered.

Choosing one of the appropriate application delivery method helps improve scalability,

management and user experience.

 Installed app – The application is part of the base desktop image. The install process

involves dll, exe and other files copied to the image drive as well as registry

modifications.

 Streamed App (Microsoft App-V) – The application is profiled and delivered to the

desktops across the network on-demand. Application files and registry settings placed in

a container on the virtual desktop and isolated from the base operating system and

each other, which helps to address compatibility issues.

 Layered App (Citrix App Layering) – Each layer contains a single application, agent or

operating system. Layering simplifies ongoing maintenance, as an OS, agent and

application exists in a single layer; update the layer and all deployed images containing

that layer are updated. App Layering has two different delivery options:

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o Layered Image – By integrating one OS layer, one platform layer

(XenApp/XenDesktop VDA, Provisioning Services agent) and many application

layers, an administrator can easily create new, deployable images.

o Elastic Layer – A XenApp and XenDesktop user can dynamically receive a new

app layer based at logon. On a XenApp host, an elastic layer is session-aware,

where an attached layer is only available to a user’s session granted access to

the layer.

 Hosted Windows App - An application installed on a multi-user XenApp host and

deployed as an application and not a desktop. A user accesses the hosted Windows app

seamlessly from the VDI desktop or endpoint device, hiding the fact that the app is

executing remotely.

 Local App – An application deployed on the endpoint device. The application interface

appears within the user’s hosted VDI session even though it executes on the endpoint.

The following table provides recommendations on the preferred approaches for integrating

applications into the overall solution,

App Category

Installed App

Streamed

App

Layered App

Hosted

Windows App

Local App

Common





Departmental





User





Management









“”: Recommended, ““: Not Recommended, “º” Viable

Table 29: App Deployment Recommendations

Virtual Machines

Virtual resources require proper allocation of the processor, memory and disk. These decisions have

a direct impact on the amount of hardware required as well as the user experience.

The key to successful resource allocation is to ensure that virtual desktops and applications offer

similar levels of performance to physical desktops. Otherwise, productivity and overall user

satisfaction will be affected. Allocating resources to the virtual machines above their requirements

however is inefficient and expensive for the business.

The resources allocated should be based on the workload characteristic of each user group,

identified during the assess phase.

Experience from the Field

Energy – An energy company installs applications on the base image for the majority of

users and streams departmental applications as required.

Financial – A banking customer maintains and deploys multiple desktop images containing

user group focused applications as required by various departments.

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Decision: Virtual Processor (vCPU)

For hosted desktop-based VDI models (hosted pooled desktops and hosted personal desktops),

the general recommendation is two or more vCPUs per virtual machine so that multiple threads

can be executed simultaneously. Although a single vCPU could be assigned for extremely light

workloads, users are more likely to experience session hangs.

For hosted server-based VDI models (hosted Windows apps, hosted browser apps, hosted

shared desktops), the proper vCPU allocation is based on the Non-Uniform Memory Access

(NUMA) architecture of the processors.

Figure 29: NUMA Architecture

Each socket is divided into one or more NUMA nodes. Hosted server-based VDI models will often

utilize 4 or more processors. Allocating more vCPU than the NUMA node contains results in a

performance hit. Allocating a portion of a NUMA node to a virtual machine results in a

performance hit if the portion allocated is not easily divisible by the size of the NUMA node. It is

often ideal to allocate the number of cores within a NUMA node to a virtual machine or allocate

½ of the cores to a virtual machine, while doubling the number of virtual machines.

User

Workload

Operating System

vCPU

Configured for Scale

vCPU

Configured for Experience

Light

Windows 7

2 vCPU

Windows 10

2 vCPU

Windows 2012R2

NUMA or ½ of NUMA

Windows 2016

NUMA or ½ of NUMA

Medium

Windows 7

2 vCPU

3 vCPU

Windows 10

2 vCPU

3 vCPU

Windows 2012R2

NUMA or ½ of NUMA

Windows 2016

NUMA or ½ of NUMA

Heavy

Windows 7

3 vCPU

4 vCPU

Windows 10

3 vCPU

4 vCPU

Windows 2012R2

NUMA or ½ of NUMA

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Windows 2016

NUMA or ½ of NUMA

Table 30: vCPU Allocation

Note: Windows 2012R2 recommendations are based on the hosted Windows app, hosted

browser app and hosted shared desktop VDI model.

Decision: CPU Optimization

In a shared and virtualized environment, a single user can monopolize CPU resources due to a

runaway process or an intense data processing operation in Excel. If the processor is

oversubscribed, it will not be able to fulfill other users’ requests, resulting in a hung session.

Citrix Workspace Environment Management, a component of XenApp and XenDesktop,

incorporates CPU optimization. When a process consumes a certain percentage of the CPU over

a defined timeframe, the process priority lowers from normal to low or very low, giving all

remaining processes a higher priority and overcoming the runaway process risk. CPU

optimization will also remember processes that triggered CPU protection and automatically start

the process at a lower priority on future launches.

Most environments should enable CPU optimization as a default configuration.

Decision: Virtual Memory (vRAM)

The amount of memory allocated to each resource is a function of the user’s expected workload

and application footprint. Assigning insufficient memory to the virtual machines will cause

excessive paging to disk, resulting in a poor user experience; allocating too much RAM increases

the overall cost of the solution.

The following table provides guidance on the virtual RAM that should be assigned based on

workload.

User

Workload

Operating System

vRAM

Configured for Scale

vRAM

Configured for Experience

Light

Windows 7

2 GB

3 GB

Windows 10

2 GB

3 GB

Windows 2012R2

256 MB per user

Windows 2016

320 MB per user

Medium

Windows 7

3 GB

4 GB

Windows 10

3 GB

4 GB

Windows 2012R2

512 MB per user

Windows 2016

640 MB per user

Heavy

Windows 7

6 GB

8 GB

Windows 10

6 GB

8 GB

Windows 2012R2

1024 MB per user

Windows 2016

1280 MB per user

Table 31: vRAM Allocation

Note: Windows 2012R2 recommendations are based on the hosted Windows app, hosted

browser app and hosted shared desktop VDI model.

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Note: Memory allocation above 4GB requires a 64-bit operating system

Note: If used, the Machine Creation Services and Provisioning Services cache in RAM amount

should be added onto the virtual machine RAM specifications.

Decision: RAM Optimization

Even though users only work within a single application at a time, most have five or more

applications running but idle. When a process moves from active to idle, the application and

operating system releases a portion of the process’s active working set of memory to free up

system resources. However, this is only a small percentage of the applications working set. The

rest remains locked for the application, severely limiting available system resources.

Using RAM Optimization within Citrix Workspace Environment Management, applications that

are idle (have not been interacted with by a user) for a certain time are forced to release excess

memory until they are no longer idle. When the application returns to an active state, the

released memory is loaded back into the active working set.

Most environments should enable RAM optimization as a default configuration. A RAM

optimization exclusion list is available if certain processes encounter issues with optimization.

Decision: Disk Cache

The amount of storage that each VM requires will vary based on the workload and the image

type. If creating hosted personal desktop without leveraging an image management solution,

each VM will require enough storage for the entire OS and locally installed applications.

Deploying machines through Machine Creation Services or Provisioning Services can

substantially reduce the storage requirements for each virtual machine. Disk space requirements

for the write cache and difference disk will depend on application usage and user behavior.

However, the following table provides a starting point for estimating disk space requirements

based on machine sized with vCPU and vRAM as per the guidelines above:

User

Workload

Operating System

Storage Space

(Differencing Disk / Write Cache Disk)

Light

Windows 7

10 GB

Windows 10

10 GB

Windows 2012R2

40 GB

Windows 2016

60 GB

Medium

Windows 7

15 GB

Windows 10

15 GB

Windows 2012R2

40 GB

Windows 2016

60 GB

Heavy

Windows 7

20 GB

Windows 10

20 GB

Windows 2012R2

40 GB

Windows 2016

60 GB

Table 32: Disk Cache Allocation

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Decision: RAM Cache

Provisioning Services and Machine Creation Services have the capability to utilize a portion of the

virtual machine’s RAM as a buffer for the storage cache. The RAM cache is used to improve the

performance of traditional storage by sharing the virtual machine’s non-paged pool memory

User

Workload

Operating System

RAM Cache

Configured for Scale

RAM Cache

Configured for Experience

Light

Windows 7

128 MB

256 MB

Windows 10

128 MB

256 MB

Windows 2012R2

2 GB

Windows 2016

4 GB

Medium

Windows 7

256 MB

512 MB

Windows 10

256 MB

512 MB

Windows 2012R2

4 GB

Windows 2016

8 GB

Heavy

Windows 7

512 MB

1024 MB

Windows 10

512 MB

1024 MB

Windows 2012R2

6 GB

Windows 2016

10 GB

Table 33: RAM Cache Allocation

Note: If used, the Machine Creation Services and Provisioning Services cache in RAM amount

should be added onto the virtual machine RAM specifications.

Note: If additional RAM is available on the host, the RAM Cache amounts can be increased to

provide even greater levels of performance.

Decision: Storage IOPS

Storage performance is limited by the number of operations it can handle per second, referred

to as IOPS. Under allocating storage IOPS results in a VDI desktop where apps, web pages and

data are slow to load.

The following table provides guidance on the number of storage IOPS generated per user based

on workload and operating system. Storage IO activity will be higher during user logon/logoff.

User

Workload

Operating System

Storage IOPS

(without RAM-Based

Cache)

Storage IOPS

(with RAM-Based

Cache)

Light

Windows 7

10 IOPS

1 IOPS

Windows 10

12 IOPS

1 IOPS

Windows 2012R2

3 IOPS

0.5 IOPS

Windows 2016

4 IOPS

1 IOPS

Medium

Windows 7

15 IOPS

1 IOPS

Windows 10

20 IOPS

1.5 IOPS

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Windows 2012R2

4 IOPS

0.5 IOPS

Windows 2016

6 IOPS

1 IOPS

Heavy

Windows 7

25 IOPS

2 IOPS

Windows 10

35 IOPS

3 IOPS

Windows 2012R2

5 IOPS

0.5 IOPS

Windows 2016

8 IOPS

1 IOPS

Table 34: IOPS Allocation

Decision: IO Prioritization

With shared environments, every user’s IO process receives an equal share of resources. A user

running some IO intensive task can affect mission critical applications. Citrix Workspace

Environment Management allows administrators to define IO priorities for processes.

If a process requires more IO resources or the process is monopolizing IO resources, the process

and process priority is manually increased or decreased via the console. This advanced

configuration is only used in special circumstances.

Decision: Graphics (GPU)

Without a graphical processing unit (GPU), graphical processing is rendered with software by the

CPU. A graphical processing unit (GPU) can be leveraged to improve server scalability and user

experience or enable the use of graphically intensive applications. During the desktop design it is

important to decide how the GPU (if used) will be mapped to the virtual machines. There are

three methods available.

 Pass-Through GPU – Each physical GPU is passed through to a single virtual machine

(hosted apps or hosted desktops).

 Hardware Virtualized GPU – Using a hypervisor’s vGPU technology, an NVIDIA GRID or

Intel Iris Pro is virtualized and shared between multiple machines. Each virtual machine

has the full functionality of GPU drivers and direct access to the GPU.

 Software Virtualized GPU – The GPU is managed by the hypervisor and intercepts

requests made by the VDI desktops. This process is used if a GPU is not installed within

the host.

Pass-

Through

GPU

Hardware

Virtualized

GPU (NVidia)

Hardware

Virtualized

GPU (Intel)

Hardware

Virtualized

GPU (AMD)

Software

Emulated

GPU

Citrix XenServer

XenDesktop







XenApp







Microsoft Hyper-V

XenDesktop







XenApp







VMware vSphere

XenDesktop







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XenApp







“”: Available ““: Not Supported

Table 35 GPU Allocation Options

User groups with a heavy use of graphical applications will often require the use of a NVidia

hardware virtualized GPU. User groups who rely on office-based applications can have an

observable benefit with the use of a hardware virtualized GPU from Intel.

Layer 4: The Control Layer

Active Directory

Decision: Forest Design

Multi-forest deployments, by default, do not have inter-domain trust relationships between the

forests. An AD administrator can establish trust relationships between the multiple forests,

allowing the users and computers from one forest to authenticate and access resources in

another forest.

For forests that have inter-domain trusts, it is recommended that the appropriate settings be

configured to allow the Delivery Controllers to communicate with both domains. When the

appropriate trusts are not configured, multiple XenDesktop sites for each forest must be

configured. This section outlines the storage requirements on a per product basis and provides

sizing calculations. For more information, please refer to Citrix article: CTX134971 – Successfully

Deploying XenDesktop in a Complex Active Directory Environment

Decision: Organizational Unit Structure

Infrastructure components for a XenApp and XenDesktop deployment should reside within their

own dedicated organizational units (OUs); separating workers and controllers for management

purposes. By having their own OUs, the objects inside will have greater flexibility with their

management while allowing Citrix administrators to be granted delegated control.

A sample Citrix OU structure can be seen below.

Citrix

Citrix Infrastructure

Delivery Controllers

Provisioning Services Servers

StoreFront Servers

Citrix VDAs

Desktop OS

Server OS

Figure 30: Example Citrix OU Structure

Decision: User Groups

Whenever possible, permissions and authorization should be assigned to user groups rather

than individual users, thereby eliminating the need to edit a large amount of resource

permissions and user rights when creating, modifying, or deleting user accounts.

Permission application example:

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 An application published to one group of 1,000 users requires the validation of only one

object for all 1,000 users.

 The same application published to 1,000 individual user accounts requires the validation

of all 1,000 objects.

Database

The majority of Citrix products discussed within this document require a database. The following

table outlines the usage on a per product basis:

Product

Configuration

Data

Runtime Data

Audit / Change

Log Data

Monitoring

Data

XenDesktop



Provisioning Services







DesktopPlayer



“”: Optional

Table 36: Database usage

Decision: Edition

There are multiple editions of Microsoft SQL Server 2012: Express, Web, Standard, Business

Intelligence, and Enterprise. Based on the capabilities of the various SQL Server editions available,

the Standard edition is often used for hosting the XenApp and XenDesktop databases in

production environments.

The Standard edition provides an adequate amount of features to meet the needs of most

environments. For more information on the databases supported with Citrix products please

refer to the Citrix Database Support Matrix. Different versions of Citrix products support different

versions of the SQL server; therefore, it is important to check the support matrix to ensure the

version of SQL server used is compatible with the Citrix product being deployed.

Decision: Database Server Sizing

The SQL server must be sized correctly to ensure the performance and stability of an environment.

Since every Citrix product uses SQL server in a different way, no generic all-encompassing sizing

recommendations can be provided. Instead, per-product SQL server sizing recommendations are

provided below.

XenApp and XenDesktop

XenApp and XenDesktop Brokers use the database as a message bus for broker

communications, storing configuration data and storing monitoring and configuration log data.

The databases are constantly in use and the performance impact on the SQL server can be

considered as high.

Based on results from Citrix internal scalability testing the following SQL server specification for a

server hosting all XenDesktop databases are recommended:

 2 Cores / 4 GB RAM for environments up to 5,000 users

 4 Cores / 8 GB RAM for environments up to 15,000 users

 8 Cores / 16 GB RAM for environments with 15,000+ users

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The database files and transaction logs should be hosted on separate hard disk subsystems in

order to cope with a high number of transactions. For example, registering 20,000 virtual

desktops during a 15-minute boot storm causes ~500 transactions / second and 20,000 users

logging on during a 30-minute logon storm causes ~800 transactions / second on the

XenDesktop Site Database.

Provisioning Services

In addition to static configuration data provisioning servers store runtime and auditing

information in the database. Depending on the boot and management pattern, the

performance impact of the database can be considered as low to medium.

Based on this categorization, a SQL server specification of 4 Cores and 4 GB RAM is

recommended as a good starting point. The SQL server should be carefully monitored during the

testing and pilot phase in order to determine the optimal configuration of the SQL server.

Decision: Instance Sizing

When sizing a SQL database, two aspects are important:

 Database file – Contains the data and objects such as tables, indexes, stored procedures

and views stored in the database.

 Transaction log file – Contains a record of all transactions and database modifications

made by each transaction. The transaction log is a critical component of the database

and, if there is a system failure, the transaction log might be required to bring the

database back to a consistent state. The usage of the transaction log varies depending

on which database recovery model is used:

o Simple recovery – No log backups required. Log space is automatically

reclaimed, to keep space requirements small, essentially eliminating the need to

manage the transaction log space. Changes to the database since the most

recent backup are unprotected. In the event of a disaster, those changes must

be redone.

o Full recovery – Requires log backups. No work is lost due to a lost or damaged

database data file. Data of any arbitrary point in time can be recovered (for

example, prior to application or user error). Full recovery is required for database

mirroring.

o Bulk-logged – Requires log backups. This is an adjunct of the full recovery model

that permits high-performance bulk copy operations. It is typically not used for

Citrix databases.

For further information, please refer to the Microsoft Developer Network – SQL Server

Recovery Models.

In order to estimate storage requirements, it is important to understand the disk space

consumption for common database entries. This section outlines the storage requirements on a

per product basis and provides sizing calculations. For more information, please refer to Citrix

article: CTX139508 – XenDesktop 7.x Database Sizing.

XenDesktop General

XenApp 7.x and XenDesktop 7.x use three distinct databases:

 Site Configuration database – Contains static configuration and dynamic runtime data

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 Monitoring database – Contains monitoring data which is accessible via Director

 Configuration logging database – Contains a record for each administrative change

performed within the site (accessible via Studio)

Site Database

Since the database of a XenApp or XenDesktop site contains static configuration data and

dynamic runtime data, the size of the database file depends not only on the physical size of the

environment but also user patterns. The following factors all impact the size of the database file:

 The number of connected sessions

 The number of configured and registered VDAs

 The number of transactions occurring during logon

 VDA heartbeat transactions

The size of the Site Database is based on the number of VDAs and active sessions. The following

table shows the typical maximum database size Citrix observed when scale testing XenApp and

XenDesktop with a sample number of users, applications, and desktop delivery methods.

Users

Applications

Desktop Types

Expected Maximum Size (MB)

1,000

Hosted Shared

10,000

100

Hosted Shared

100,000

200

Hosted Shared

330

1,000

N/A

Hosted Pooled

10,000

N/A

Hosted Pooled

115

40,000

N/A

Hosted Pooled

390

Table 37: XenDesktop Site DB sample size calculations

Note: This sizing information is a guide only. Actual database sizes may differ slightly by

deployment due to how databases are maintained.

Determining the size of the transaction log for the Site database is difficult due to factors that

can influence the log including:

 The SQL Database recovery model

 Launch rate at peak times

 The number of desktops being delivered

During XenDesktop scalability testing, Citrix observed the transaction log growth rate at 3.5MB

an hour when the system is idle, and a per user per day growth rate of ~32KB. In a large

environment, transaction log usage requires careful management and a regular backup, to

prevent excessive growth. This can be achieved by means of scheduled jobs or maintenance

plans

Monitoring Database

Of the three databases, the Monitoring database is expected to be the largest since it contains

historical information for the site. Its size is dependent on many factors including:

 Number of Users

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 Number of sessions and connections

 Number of workers

 Retention period configuration – Platinum customers can keep data for over a year

(default 90 days). Non-platinum customers can keep data for up to 7 days (default 7

days).

 Number of transaction per second. Monitoring service tends to execute updates in

batches. It is rare to have the number of transactions per second go above 20.

 Background transaction caused by regular consolidation calls from the Monitoring

service.

 Overnight processing carried out to remove data outside the configured retention

period.

The following table shows the estimated size of the Monitoring database over a period of time

under different scenarios. This data is an estimate based on data seen within scale testing

XenApp and XenDesktop (assuming a 5 day working week).

Estimates with 1 connection and 1 session per user with a 5 day work week

Users

Type

1 week (MB)

1 month (MB)

3 months (MB)

1 year (MB)

1,000

HSD

230

900

10,000

HSD

160

600

1,950

7,700

100,000

HSD

1,500

5,900

19,000

76,000

1,000

VDI

170

670

10,000

VDI

120

440

1,400

5,500

40,000

VDI

464

1,700

5,400

21,500

Estimates with 2 connections and 1 session per user with a 5 day work week

Users

Type

1 week (MB)

1 month (MB)

3 months (MB)

1 year (MB)

1,000

HSD

100

330

1,300

10,000

HSD

240

925

3,000

12,000

100,000

HSD

2,400

9,200

30,000

119,000

1,000

VDI

280

1,100

10,000

VDI

200

750

2,500

9,800

40,000

VDI

800

3,000

9,700

38,600

Table 38: Monitoring DB size estimations

Note: The 100,000 HSD tests are based on a test environment consisting of:

 2 Delivery Controllers

 43 Hosted Shared Desktop workers

 3 SQL servers, configured with databases held within one Always On Availability Group.

For more information please see the Citrix Support article – XenDesktop 7.x Database Sizing.

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The size of the transaction log for the Monitoring Database is very hard to estimate, but XenApp

and XenDesktop scalability testing showed a growth rate of about 30.5 MB an hour when the

system is idle, and a per user per day growth rate of ~9 KB.

Configuration Logging Database

The Configuration Logging Database is typically the smallest of the three databases. Its size and

the size of the related transaction log depends on the daily administrative activities initiated from

Studio, Director or PowerShell scripts, therefore its size is difficult to estimate. The more

configuration changes are performed, the larger the database will grow. Some factors that can

affect the size of the database include:

 The number of actions performed in Studio, Director and PowerShell.

 Minimal transactions which occur on the database when no configuration changes are

taking place.

 The transaction rate during updates. Updates are batched whenever possible.

 Data manually removed from the database. Data within the Configuration Logging

Database is not subject to any retention policy, therefore it is not removed unless done so

manually by an administrator.

 Activities that have an impact on sessions or users, for example, session logoff and reset.

 The mechanism used for deploying desktops.

In XenApp environments not using MCS, the database size tends to fall between 30 and 40MB. For

MCS environments, database size can easily exceed 200MB due to the logging of all VM build data.

Temporary Database

In addition to the Site, Monitoring, and Configuration Logging databases, a system-wide

temporary database (tempdb) is provided by SQL Server. This temporary database is used to store

Read-Committed Snapshot Isolation data. XenApp 7.x and XenDesktop 7.x uses this SQL Server

feature to reduce lock contention on the XenApp and XenDesktop databases. Citrix recommends

that all XenApp 7.x and XenDesktop 7.x databases use Read-Committed Snapshot Isolation. For

more information please see How to Enable Read-Committed Snapshot in XenDesktop.

The size of the tempdb database will depend on the number of active transactions, but in general

it is not expected to grow more than a few MBs. The performance of the tempdb database does

not impact the performance of XenApp and XenDesktop brokering, as any transactions that

generate new data require tempdb space. XenApp and XenDesktop tend to have short-lived

transactions, which help keep the size of the tempdb small.

The tempdb is also used when queries generate large intermediate result sets. Guidance and

sizing the tempdb can be found on the Microsoft TechNet article Optimizing tempdb

Performance.

Provisioning Services

The Provisioning Services farm database contains static configuration and configuration logging

(audit trail) data. The record size requirements outlined below can be used to help size the

database:

Configuration Item

DB Space

Required (KB)

Number of

Items (Example)

Total (KB)

Base farm configuration

112

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User group w/ farm access

250

Site

Device collection

500

Farm view

Farm view to device relationship

5,000

Site View

Site view to device relationship

5,000

Device

5,000

10,000

Device bootstrap

Device to disk relationship

175,000

Device printer relationship

Device personality data

Device status (when booted)

5,000

Device custom property

vDisk

vDisk version

300

Disk locator

200

Disk locator custom property

Server

Server IP

Server status (when booted)

Server custom property

vDisk store

vDisk store to server relationship

Connection to XenServer

(VirtualHostingPool)

vDisk update task

100

Administrative change (auditing

enabled)

10,000

Total

211,732KB

(~212MB)

Table 39: Provisioning Services Farm DB sample size calculations

During the PVS farm setup, a database with an initial file size of 20MB is created. Due to the nature

of the data in the PVS farm database the transaction log is not expected to grow very quickly,

unless a large amount of configuration is performed.

In contrast to XenApp, which also offers the ability to track administrative changes, the related

information is not written to a dedicated database but directly to the Provisioning Services farm

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database. In order to limit the size of the Provisioning Services database it is recommended to

archive the audit trail data on a regular schedule.

Decision: Database Location

By default, the Configuration Logging and Monitoring databases are located within the Site

Configuration database. Citrix recommends changing the location of these secondary databases

as soon as the configuration of the site has been completed, in order to simplify sizing,

maintenance and monitoring. All three databases can be hosted on the same server or on

different servers. An ideal configuration would be to host the Monitoring database on a different

server from the Site Configuration and Configuration Logging databases since it records more

data, changes occur more frequently and the data is not considered to be as critical as the other

databases. For more information, please refer to Citrix Docs – Change secondary database

locations.

Note: The location of the Configuration Logging database cannot be changed when mandatory

logging is enabled.

Decision: High-Availability

The following table highlights the impact to XenApp, XenDesktop and Provisioning Services when

there is a database outage:

Component

Impact of Database Outage

Site configuration

database

Users will be unable to connect or reconnect to a virtual desktop.

Note: Local Host Cache allows users with Hosted Shared Desktops,

Hosted Windows and Browser Applications, and Personal Desktops to

reconnect to their applications and desktops even when the site

database is unavailable.

Monitoring database

Director will not display any historical data and Studio cannot be started.

Brokering of incoming user requests and existing user sessions will not

be affected.

Configuration logging

database

If allow changes when the database is disconnected has been enabled

within XenApp and XenDesktop logging preferences, an outage of the

configuration logging database will have no impact (other than

configuration changes not being logged). Otherwise, administrators will

be unable to make any changes to the XenApp and XenDesktop site

configuration. Users are not impacted.

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Provisioning Services

farm database

When offline database support is enabled and the database becomes

unavailable, the stream process uses a local copy of the database to

retrieve information about the provisioning server and the target devices

supported by the server. This allows provisioning servers and the target

devices to remain operational. However, when the database is offline,

the console and the management functions listed below become

unavailable:

 Auto Add target devices

 vDisk creation and updates

 Active Directory password changes

 Stream process startup

 Image update service

 PowerShell and MCLI based management

If offline database support has not been enabled, all management

functions become unavailable and the boot and failover of target

devices will fail.

Table 40: Impact of a database outage

Note: Please review HA options for 3

party databases (for example, App-V, SCVMM or vCenter)

with the respective software vendor.

In addition to the built-in database redundancy options, Microsoft SQL Server, as well as the

underlying hypervisor (in virtual environments), offer a number of high availability features. These

enable administrators to ensure single server outages will have a minimal impact (if any) on the

XenApp and XenDesktop infrastructure. The following the SQL / hypervisor high availability

features are available:

 VM-level HA – This high availability option is available for virtual SQL servers only, which

need to be marked for High Availability at the hypervisor layer. In case of an unexpected

shutdown of the virtual machine or the underlying hypervisor host, the hypervisor will try

to restart the VM immediately on a different host. While VM-level HA can minimize

downtimes in power-outage scenarios, it cannot protect from operating system level

corruption. This solution is less expensive than mirroring or clustering because it uses a

built-in hypervisor feature. However, the automatic failover process is slower, as it can take

time detect an outage and start the virtual SQL server on another host. This may interrupt

the service to users.

 Mirroring – Database mirroring increases database availability with almost instantaneous

failover. Database mirroring can be used to maintain a single standby or mirror database,

for a corresponding principal or production database. Database mirroring runs with either

synchronous operation in high-safety mode, or asynchronous operation in high-

performance mode. In high-safety mode with automatic failover (recommended for

XenDesktop) a third server instance, known as a witness, is required, which enables the

mirror server to act as a hot standby server. Failover from the principal database to the

mirror database happens automatically and is typically completed within a few seconds. It

is a good practice to enable VM-level HA (or a similar automatic restart functionality) for at

least the witness to ensure SQL service availability in case of a multi-server outage.

Note: Microsoft is planning to remove mirroring as a high availability option in a future

release of SQL Server and is discouraging its use in new network development. Please refer

to the Microsoft article – Database Mirroring (SQL Server) for more information.

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 AlwaysOn Failover Cluster Instances – Failover clustering provides high-availability support

for an entire instance of Microsoft SQL Server. A failover cluster is a combination of two or

more nodes, or servers, using a shared storage. A Microsoft SQL Server AlwaysOn Failover

Cluster Instance, introduced in SQL Server 2012, appears on the network as a single

computer, but has functionality that provides failover from one node to another if the

current node becomes unavailable. The transition from one node to the other node is

seamless for the clients connected to the cluster. AlwaysOn Failover cluster Instances

require a Windows Server Failover Clustering (WSFC) resource group. The number of

nodes supported in the WSFC resource group will depend on the SQL Server edition.

(Please refer to the table in the Decision: Edition earlier in this chapter.) For more

information please refer to MSDN – AlwaysOn Failover Cluster Instances (SQL Server).

 AlwaysOn Availability Groups – AlwaysOn Availability Groups is an enterprise-level high-

availability and disaster recovery solution introduced in Microsoft SQL Server 2012, which

enables administrators to maximize availability for one or more user databases. AlwaysOn

Availability Groups require that the Microsoft SQL Server instances reside on Windows

Server failover clustering (WSFC) nodes. Similar to failover clustering a single virtual IP /

network name is exposed to the database users. In contrast to failover clustering, shared

storage is not required since the data is transferred using a network connection. Both

synchronous and asynchronous replication to one or more secondary servers is supported.

As opposed to mirroring or clustering secondary servers can be actively used for

processing incoming read-only requests, backups or integrity checks. This feature can be

used to offload user resource enumeration requests to a secondary SQL server in

XenDesktop environments to essentially scale-out a SQL server infrastructure. Since the

data on active secondary servers can lag multiple seconds behind the primary server, the

read-only routing feature cannot be used for other XenDesktop database requests at this

point in time. For more information, please refer to MSDN – AlwaysOn Availability Groups

(SQL Server).

The following table outlines the recommended high availability features for Citrix databases:

Component

VM-Level

Mirroring

AlwaysOn

Failover Cluster

Instances

AlwaysOn

Availability

Groups

Site database





Configuration logging

database



Monitoring database





Provisioning Services farm

database







DesktopPlayer database





“”: Recommended “º”: Viable ““: Not Supported “”: Recommended for test environments only

Table 41: Recommended SQL high availability options

Citrix Licensing

Citrix offers organizations the flexibility of multiple licensing models that align with common usage

scenarios. The different licensing models vary based on the Citrix product used, but can include per

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user/device and per concurrent user. Several Citrix products use the license server, while other

products require a license to be installed on the product itself.

Product

License Location

XenDesktop

Citrix License Server

XenApp

Citrix License Server

Provisioning Services

Citrix License Server

XenServer

Citrix License Server

NetScaler

On the product

NetScaler Gateway

On the product

For more information on XenDesktop 7.x licensing, please refer to CTX128013 - XenDesktop

Licensing.

For more information on Microsoft Licensing, please refer to the Microsoft document – Licensing

Microsoft’s Virtual Desktop Infrastructure Technology.

Decision: Sizing

Internal scalability testing has shown that a single virtual license server with two cores and 2GB

of RAM can issue approximately 170 licenses per second or 306,000 licenses per half hour. If

necessary, the specification of the license server can be scaled out to support a higher number of

license requests per second.

Decision: High Availability

For a typical environment, a single license server is sufficient. Should the license server become

unavailable, dependent Citrix products will enter a 30-day grace period, which provides more

than enough time to resolve connectivity issues and/or restore or rebuild the license server.

Note: If the license server and the Citrix product do not communicate within 2 heartbeats (5-10

min), the Citrix product will enter a grace period and will allow connections for up to 30 days.

Once communication with the license server is re-established, the license server will reconcile the

temporary and actual licenses.

Note: A CNAME record in DNS is a convenient way to reference the license server. Using CNAMEs

allows the license server name to be changed without updating the Citrix products.

If additional redundancy is required, Citrix supports the following high availability solutions for

the license server.

 Windows Clustering – Cluster servers are groups of computers that work together in

order to increase availability. Clustering allows the license server role to automatically

failover in the event of a failure. For more information on clustering, please see the Citrix

Docs article – Clustered License Servers.

 Duplication of license server – Create a VM level backup of the license server. This

backup should not be stored on the same host as the license server. Instead, it should be

stored in a safe location, such as a highly available storage solution, or backed up to tape

or disk. The duplicate server is not active, and will remain on standby until the need arises

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to restore the active license server. Should the license server be restored using this

backup, any new licenses must be re-downloaded to the server.

For more information, please refer to Citrix eDocs – Licensing Architecture Overview.

Each method allows an administrator to exchange a single license server for another without an

interruption in service; assuming that the change occurs during the grace period and that the

following limitations are considered.

 License files will reference the server specified during the allocation process. This means

that the license files can only be used on a server with the same binding information

(Hostname) as the server that was previously specified.

 Two Windows-based, domain joined license servers cannot share the same name and

be active in the environment at the same time.

 Because license servers do not communicate with each other, any additional licenses

must be placed on both the active and backup license server.

Decision: Optimization

License server performance can be optimized by tuning the number of “receive” and

“processing” threads. If the thread count is set too low, requests will be queued until a thread

becomes available. Conversely, if the thread count is set too high, the license server will become

overloaded.

The optimal values are dependent on the server hardware, site configuration, and license request

volume. Citrix recommends testing and evaluating different values to determine the proper

configuration. Setting the maximum number of processing threads to 30 and the maximum

number of receiving threads to 15 is a good starting point for large scale deployments.

This optimization will improve the Citrix License Server ‘s ability to provide licenses by increasing

its ability to receive and process license requests.

For more information, please refer to the Citrix Docs – Improving Performance by Specifying

Thread Use

Delivery Controllers

Decision: Server Sizing

Delivery Controller scalability is based on CPU utilization. The more processor cores available, the

more virtual desktops a controller can support. Each desktop startup, registration, enumeration

and launch request impacts the controller’s processor. As the storm increases in intensity, the

CPU utilization of the controller will increase. If the CPU reaches a critical threshold, roughly 80%,

the site will need to either scale up or scale out.

Adding additional CPU cores to a Delivery Controller will lower the overall CPU utilization, thus

allowing for greater numbers of desktops supported by a single controller. This is really only

feasible when dealing with virtualized controllers as adding virtual CPUs is fairly easy and

straightforward. The other alternative is to add another controller into the site configuration. The

controller would have the same configuration as other controllers, and the load would be evenly

distributed across all controllers, thus helping to reduce the overall load on each single

controller.

Testing has shown that a single Delivery Controller, using the following configuration, can

support more than 5,000 desktops.

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Component

Specification

Processor

4 vCPU

Memory

4GB RAM

Network

Bonded virtual NIC

Host Storage

40GB shared storage

Operating System

Windows Server 2012R2

XenDesktop

Table 42: Delivery Controller Specification for 5K Sessions

The following formula can be used to calculate the number of Delivery Controllers required for a

Citrix site.

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Decision: High Availability

If the server hosting the Delivery Controller is unavailable, users will not be able to access their

virtual desktops or published applications. Therefore at least two Delivery Controllers (N+1

redundancy) should be deployed per zone on different physical servers to prevent this

component from becoming a single point of failure. If one controller fails, the others can

manage connections and administer the site.

The locations of all Delivery Controllers are specified on the VDA, allowing it to automatically

failover if communication with one Delivery Controller is unavailable. The VDA checks the

following locations, in order, stopping at the first place it finds the Delivery Controller:

1. A persistent storage location maintained for the auto-update feature. This location

contains controller information when auto-update is enabled and after the VDA

successfully registers for the first time after installation.

For its initial registration after installation, or when auto-update is disabled, the VDA checks the

following locations.

2. Policy settings (Delivery Controllers, Delivery Controller SIDs).

3. The Delivery Controller information under the VDA ListofDDCs registry key. The VDA

installer initially populates these values, based on the information specified when

installing the VDA.

4. OU-based discovery. This is a legacy method maintained for backward compatibility.

5. The Personality.ini file created by Machine Creation Services.

Citrix Consulting recommends utilizing the auto-update feature (enabled by default). This

feature will simplify management of the environment by keeping VDA’s updated when adding

and removing Delivery Controllers.

Decision: Local Host Cache

Even if the SQL database is highly available, there is the risk of not having access to the database if

the network connection between the delivery controller and SQL database fails, which is an

important concern for sites that span geographical locations.

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To overcome this risk, the delivery controllers can utilize the local host cache feature that creates a

local copy of the SQL database, used only if the delivery controller loses contact with the database.

The following must be considered when using local host cache:

 Elections – When the zones loses contact with the SQL database, an election occurs

nominating a single delivery controller as master. All remaining controllers go into idle

mode. A simple alphabetical order determines the winner of the election.

 Sizing – When using local host cache mode, a single delivery controller is responsible for

all VDA registrations, enumerations, launches and updates. The elected controller must

have enough resources (CPU and RAM) to handle the entire load for the zone. A single

controller can scale to 10,000 users, which influences the zone design.

o RAM – The local host cache services can consume 2+GB of RAM depending on the

duration of the outage and the number of user launches during the outage.

o CPU – The local host cache can use up to 4 cores in a single socket.

o Storage – During local host cache mode, storage space increased 1MB every 2-3

minutes with an average of 10 logons per second.

 Power Options – Powered off virtual resources will not start when the delivery controller is

in local host cache mode. Pooled virtual desktops that reboot at the end of a session are

placed into maintenance mode.

 Consoles – When using local host cache mode, Studio and PowerShell are not available.

Decision: XML Service Encryption

In a typical session, the StoreFront server passes credentials to the Citrix XML Service on a

Delivery Controller. The Citrix XML protocol uses clear text to exchange all data, with the

exception of passwords, which are transmitted using obfuscation.

If the traffic between the Storefront servers and the XenDesktop Controllers can be intercepted

it will be vulnerable to the following attacks:

 Attackers can intercept the XML traffic and steal resource set information and tickets.

 Attackers with the ability to crack the obfuscation can obtain user credentials.

 Attackers can impersonate the XenDesktop Controller and intercept authentication

requests.

For most organizations, the Citrix XML traffic will be isolated on a dedicated physical or virtual

datacenter network making interception unlikely. However, for safety consider using SSL

encryption to send StoreFront data over a secure HTTP connection.

Decision: Server OS Load Management

Default Load Management policies are applied to all Server OS delivery groups. The default

settings specify the maximum number of sessions a server can host at 250 and do not consider

CPU and Memory usage. Capping session count does not provide a true indication of load, which

can lead to an overburdening of Server OS delivery groups resulting in a degradation of

performance or an underutilization of Server OS delivery groups resulting in an inefficient usage

of resources.

Citrix Consulting recommends creating unique “custom” Load Management policies for each

Delivery Group based on performance and scalability testing. Different rules and thresholds can

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be applied to each Delivery Group depending on the different resource bottlenecks identified

during testing. For more information on the available Load Management policy configurations

refer to Citrix Docs – Load Management policy settings.

If adequate testing cannot be performed prior to production, Citrix Consulting recommends

implementing the following “custom“ Load Management policy which can be applied to all

servers as a baseline:

 CPU Usage - Full Load: 80%

 CPU usage excluded process priority – Below Normal or Low

 Memory Usage - Full Load: 80%

 Memory Usage base load – Report zero load (MBs): 786

 Maximum number of sessions – X

The “Maximum number of sessions” policy is included for capping purposes – this is considered a

best practice for resiliency. Organizations can choose an initial value of 250 (denoted by “X‟

above). It is highly recommended that this value and others be customized based on the results

from scalability testing.

Cloud Connector

The XenApp and XenDesktop Service within Citrix Cloud utilize a set of services contained within the

Citrix Cloud Connector. A redundant set of Cloud Connector virtual machines must be placed in

each data center/resource location containing VDA hosts.

Decision: Server Sizing

Cloud Connector scalability is based on CPU utilization. The more processor cores available, the

more virtual desktops a cloud connector can support. Each desktop startup, registration,

enumeration and launch request affects the cloud connector’s processor. As the storm increases

in intensity, the CPU utilization of the cloud connector will increase. If the CPU reaches a critical

threshold, roughly 80%, the site will need to either scale up or scale out.

Testing has shown that a single Cloud Connector Controller, using the following configuration,

can support 5,000 desktops.

Component

On-Premises Specification

Azure Hosted Specifications

Number of VMs

(with N+1 Fault Tolerance)

6 Standard_A2_V2 instances

Processors per VM

4 vCPU

2 vCPU

Memory per VM

4GB RAM

Host Storage per VM

40GB shared storage

20GB temp storage

Operating System

Windows Server 2012R2

Table 43: Cloud Connector Specification for 5K Sessions

Provisioning Services

Citrix Provisioning Services (PVS) uses streaming technology to simplify the deployment of virtual

and physical machines. Computers are provisioned and re-provisioned in real-time from a single

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shared-disk image. In doing so, administrators can completely eliminate the need to manage and

patch individual systems. Instead, all image management is performed on the master image.

Decision: Topology

A Provisioning Services farm represents the top level of the Provisioning Services infrastructure,

which can be further broken down into sites. All provisioning servers in a farm share the same

SQL database and Citrix license server.

Each site is a logical entity containing provisioning servers, vDisk pools and target device

collections. Although all sites within a farm share the same database, target devices can only fail

over to other provisioning servers within the same site.

Figure 31: PVS Site structure

There are factors that must be considered when determining the overall Provisioning Services

topology:

 Network – Provisioning servers are constantly communicating with the farm database to

retrieve system configuration settings. Therefore, separate farms should be created for

each physical location where target devices reside, unless they are connected to the

database server by a fast and robust connection.

 Administration – Organizations may need to maintain the separation of administrative

duties at a departmental, regional or countrywide basis. Additional Provisioning Services

farms will add some complexity to the management of the environment. However, this

overhead is typically limited to initial configuration, desktop creation and image updates.

 Organization – A practical reason for building multiple sites is due to organizational

changes. For example, two companies may have recently merged through acquisition,

but need to keep resources separate while integration takes place. Configuring the

organization to use separate sites is one way to keep the businesses separate but

managed centrally through the Provisioning Services console.

Only create additional sites if the business requirements warrant it. A single site per farm is easier

to manage and requires no additional configuration.

Decision: Device Collections

Device collections provide the ability to create and manage logical groups of target devices.

Creating device collections simplifies device management by allowing actions to be performed

at the collection level rather than the target device level.

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Figure 32: Device Collection structure

Device collections can represent physical locations, subnet ranges, chassis or different

departments within an organization. Collections can also be used to logically separate

production target devices from test and maintenance ones.

Consider creating device collections based on vDisk assignment so that the status of all target

devices assigned to a particular vDisk can be quickly identified.

Decision: High Availability

Provisioning Services is a critical component of the virtual desktop infrastructure. The following

recommendations should be followed to eliminate single points of failure:

 Provisioning Server – A minimum of two provisioning servers should always be

implemented per site. Sufficient redundancy should be incorporated into the design so

that a single server failure does not reduce the total number of target devices that can

be supported per site.

The Provisioning Services boot file should be configured for high availability. Up to four

Provisioning Servers may be listed in the boot file. Target devices will try to contact the

servers in the order that they are listed. The server that responds may not necessarily be

the server that will provide streaming services to the target device. If Load Balancing is

enabled, the target device may be reassigned to another server in the site that is less

loaded than the others.

 vDisks and Storage – For vDisk stores hosted on local, Direct Attached Storage (DAS) or

Storage Area Network (SAN), replication should be used to synchronize the vDisks. If

using Network Attached Storage (NAS), ensure that the vDisks are hosted on a highly

available network share.

 Networking – The provisioning servers should have redundant NICs. If the provisioning

server is deployed as a physical server, redundant NICs should be teamed and if the

provisioning server is deployed as a virtual server, the underlying hypervisor should

incorporate redundant NICs.

Note: The target devices will only failover to NICs that are in the same subnet as the PXE

boot NIC.

Trivial File Transfer Protocol (TFTP) is a communications protocol used for transferring

configuration or boot files between machines. Provisioning services can use TFTP to deliver the

bootstrap file to target devices. There are several options available to make the TFTP service

highly available. Some of the more commonly used options are:

 DNS Round Robin – A DNS entry is created for the TFTP service with multiple A records

corresponding to the TFTP services running on the provisioning servers in the farm. This

method is not recommended since the state of the TFTP service is not monitored. Clients

could potentially be sent to a non-functioning server.

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 Hardware load balancer – Use a hardware load balancer, such as Citrix NetScaler, to

create virtual IPs that corresponds to the provisioning servers. The NetScaler can

intelligently route traffic between the provisioning servers. In the event that one of the

servers becomes unavailable, NetScaler will automatically stop routing TFTP requests to

that server. This is the best method for making TFTP highly available, but can be

complicated to setup.

 Multiple DHCP Option 66 entries – This method is easy to implement but requires a

DHCP service that supports entering multiple entries in option 66. Microsoft DHCP

server allows one option 66 entry so this method would not be feasible in environments

with Microsoft DHCP services. If using a non-Microsoft DHCP server or appliance, check

with the manufacturer to verify that multiple option 66 entries is supported.

There are other options available that can achieve the same result without having to use

TFTP:

 Proxy DHCP – Use the provisioning servers PXE service to provide the bootstrap

information. If one of the servers is down, the next available server in the farm can

provide the bootstrap information. This method requires the provisioning servers to be

on the same broadcast domain as the target devices. If there are other PXE services

running on the network (Altiris, SCCM, etc.) then multiple VLANs may be required to keep

the PXE services from interfering with each other.

 Boot Device Manager – Use the Boot Device Manager to create a bootstrap file that is

either placed on the local hard drive, or used as a bootable ISO file. If the ISO file is used,

configure the target devices to boot from the CD/DVD-ROM drive, and place the ISO file

on a highly available shared network location or local storage of each target device.

When either method is utilized, the TFTP service is not used at all.

High availability should always be incorporated into the Provisioning Services design. Although

high availability may require additional resources and increased costs, it will provide a highly

stable environment so that users experience minimal impact due to service outages.

Decision: Bootstrap Delivery

A target device initiates the boot process by first loading a bootstrap program which initializes

the streaming session between the target device and the provisioning server. There are three

methods in which the target device can receive the bootstrap program:

 Using DHCP Options –

1. When the target device boots, the target device sends a broadcast for IP

address and boot information. DHCP will process this request and provide an IP

as well as scope option settings 66 (the name or IP address of the Provisioning

Services TFTP server) and 67 (the name of the bootstrap file).

Note: If using a load balancer for the TFTP service then the address of the load

balancer is entered in option 66.

2. Using TFTP, a request for the bootstrap file is sent from the target device to the

provisioning server. The target device downloads the boot file from the

provisioning server.

3. The target device boots the assigned vDisk image.

Note: Requires UDP/DHCP Helper to be configured when targets are not on the same

subnet as the DHCP servers in order to receive PXE broadcasts.

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 Using PXE Broadcasts –

1. When a target device boots from the network, the target device sends a

broadcast for an IP address and boot information. DHCP will process this

request and provide an IP address. In addition, all provisioning servers that

receive the broadcast will return boot server and boot file name information.

The target device will merge the information received and start the boot

process.

2. Using TFTP, a request for the bootstrap file is sent from the target device to the

provisioning server which responded first. The target device downloads the boot

file from the provisioning server.

Note: Make sure no other PXE services are in use on the same subnet, such as the Altiris

PXE service, or isolate using VLANs otherwise conflicts may occur with Provisioning

Services.

Note: Requires UDP/DHCP Helper to be configured when targets are not on the same

subnet as the DHCP and PVS servers in order to receive PXE broadcasts.

 Using Boot Device Manager – The Boot Device Manager (BDM) creates a boot file that

target devices obtain through a physical CD/DVD, a mounted ISO image or as a virtual

hard disk assigned to the target device. A BDM partition can be upgraded in one of three

ways:

o by collection

o by a group of highlighted devices

o by a single device

A summary of the advantages and disadvantages for each delivery method is listed in the

following table.

Delivery Method

Advantages

Disadvantages

DHCP Options

Easy to implement.

Requires changes to production

DHCP service.

DHCP service may only allow one

option 66 entry.

Requires UDP/DHCP helper for

targets on different subnets.

PXE

Easy to implement

Can interfere with other running

PXE services on the same subnet.

Requires UDP/DHCP helper for

targets on different subnets.

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BDM ISO

Does not require PXE or

TFTP services

Extra effort required to boot

physical target devices.

BDM ISO is regarded as a single

point of failure if a single file is

used.

BDM Partition

The BDM boot partition

upgrade does not

require PXE, TFTP, or

TSB; it's considered a

single stage

bootloader, at boot

time it automatically

finds all relevant PVS

server information and

does not need external

services provided by

PXE, TFTP, or TSB.

An extra 8MB partition is created

for each target device.

Table 44: Bootstrap delivery options and advantages/disadvantages.

Note: When configuring the bootstrap file, up to four provisioning servers may be listed. The order

in which the provisioning servers appear in the list determines the order which the provisioning

servers are accessed. If the first server does not respond, the next server in the list is contacted.

Decision: vDisk Format

Provisioning Services supports the use of fixed-size or dynamic vDisks:

 Fixed-size disk – For vDisks in private mode, fixed-size prevents disk fragmentation, and

offers improved write performance over dynamic disks.

 Dynamic disk – Dynamic disks require less storage space than fixed-size disks, but offer

significantly lower write performance. Although vDisks in Shared mode do not perform

writes to the vDisk, the time required to complete vDisk merge operations will increase

with dynamic disks. This is not a common occurrence as more environments choose to

create new vDisks when updating.

Since most reads will be to the System Cache in RAM, there is no significant change in

performance when utilizing fixed-size or dynamic disks. In addition, dynamic disks require

significantly less storage space. Therefore, dynamic disks are recommended.

Decision: vDisk Replication

vDisks hosted on a local, Direct Attached Storage or a SAN must be replicated between vDisk

stores whenever a vDisk is created or changed. Provisioning Services supports the replication of

vDisks from stores that are local to the provisioning server as well as replication across multiple

sites that use shared storage. The replication of vDisks can be performed manually or

automatically:

 Manual – Manual replication is simple, but can be time consuming, depending on the

number of vDisks and vDisk stores. If an error occurs during the replication process,

administrators can catch them straight away and take the appropriate steps to resolve

them. The risk of manual replication is vDisk inconsistency across the provisioning servers

which will result in load balancing and failover to not work properly. For example, if a

vDisk is replicated across three servers and then one of the vDisks is updated, that vDisk

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is no longer identical and will not be considered if a server failover occurs. Even if the

same update is made to the other two vDisks, the timestamps on each will differ, and

therefore the vDisks are no longer identical.

 Automated – For large environments, automated replication is faster than the manual

method due to the number of vDisks and vDisk Stores required. Some automated tools,

such as Microsoft DFS-R, support bandwidth throttling and Cross File Remote

Differential Compression (CF-RDC), which use heuristics to determine whether

destination files are similar to the file being replicated. If so, CF-RDC will use blocks from

these files to minimize the amount of data transferred over the network. The risk of

automated replication is that administrator do not typically monitor replication events in

real-time and do not respond quickly when errors occur, unless the automation tool has

an alerting feature. Some tools can be configured to automatically restart the copy

process in the event of a failure. For example, Robocopy supports “resume copying” in

the event that the network connection is interrupted.

For medium and large projects, use a tool to automate vDisk replication. Select a tool that is

capable of resuming from network interruptions, copying file attributes and preserving the

original timestamp.

Note: Load balancing and high availability will not work unless the vDisks have identical

timestamps.

Decision: Server Sizing

Generally, a Provisioning Server is defined with the following specifications:

Component

Specification

Model

Virtual

Processor

4 to 8 vCPU

Memory

2GB + (# of vDisks * 2GB)

Network

10 Gbps NIC

Host Storage

40 GB shared storage

vDisk Storage

Depending on number of

images/revisions

Operating System

Windows Server 2012R2

Table 45: General Provisioning Services specifications

Model

Citrix Provisioning Services can be installed on virtual or physical servers:

 Virtual – Offers rapid server provisioning, snapshots for quick recovery or rollback

scenarios and the ability to adjust server resources on the fly. Virtual provisioning servers

allow target devices to be distributed across more servers helping to reduce the impact

from server failure. Virtualization makes more efficient use of system resources.

 Physical – Offers higher levels of scalability per server than virtual servers. Physical

provisioning servers mitigate the risks associated with virtual machines competing for

underlying hypervisor resources.

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In general, virtual provisioning servers are preferred when sufficient processor, memory, disk and

networking resources can be made available and guaranteed to be available.

Note: For high availability, ensure that virtual Provisioning Servers are distributed across multiple

virtualization hosts. Distributing the virtual servers across multiple hosts will eliminate a single

point of failure and not bring down the entire Provisioning Services farm in the event of a host

failure.

CPU

Provisioning Services is not CPU intensive. However, under allocating the number of CPUs does

impact the optimization of the network streams. The number of streams that a Provisioning

Services server can run concurrently can be determined by the following formula:

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By default, the Streaming Service is configured with 20 sequential network ports, and 8 threads

per port. Therefore, by default, a provisioning server can support 160 concurrent targets. If more

than 160 streams are required, Provisioning Services continuously switches between streaming

different target devices

Ideally, if the environment needs to support more than 160 concurrent targets, the number of

ports, and threads per port can be adjusted in the Provisioning Services console. Best

performance is attained when the threads per port is not greater than the number of cores

available on the provisioning server. If the provisioning server does not have sufficient cores, the

server will show a higher CPU utilization, and target devices waiting for requests to be processed

will have a higher read latency.

Even though Provisioning Services is not CPU intensive, allocating 2 CPUs will require a larger

contiguous network port range.

 Small environments (up to approximately 500 virtual machines) 4 vCPUs are

recommended.

 Larger environments 8 vCPUs are recommended.

RAM

The Windows operating system hosting Provisioning Services partially caches the vDisks in

memory (system cache) reducing the number of reads required from storage. Reading from

storage is significantly slower than reading from memory. Therefore, Provisioning Servers should

be allocated sufficient memory to maximize the benefit from this caching process.

The following formula can be used to determine the optimal amount of memory that should be

allocated to a provisioning server:

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

  



Network

Unlike most other XenApp and XenDesktop components, Provisioning Services does not

bottleneck the CPU. Provisioning Services scalability is based on network throughput.

The following table shows the approximate amount of data that Provisioning Services requires

to boot different operating systems:

Operating System

Avg Boot Data

Usage (MB)

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Windows 10 x64

240

Windows 8 x86

178

Windows 8 x64

227

Windows 7 x86

166

Windows 7 x64

210

Windows 2012

225

Windows 2012 R2

232

Windows 2008 R2

251

Windows Vista x86

190

Windows Vista x64

240

Table 46: Approximate boot data usage by OS

Determining how much time will be required to boot the target devices can be estimated using

the following formula:

 



  





Operating System

Number of VMs

Network Throughput

Time to Boot

Windows 10 x64

500

1 Gbps

960 Seconds

(16 minutes)

Windows 10 x64

500

10 Gbps

96 Seconds

(1 minute, 36 seconds)

Table 47: Boot time estimate

A 10Gbps network is recommended for use with Provisioning Services. If a 10Gbps network is not

available, consider link aggregation to provide additional bandwidth to the provisioning servers,

or a dedicated physical streaming network.

Tip: Firewalls can add latency and create bandwidth bottlenecks in Provisioning Services

environments. If the use of firewalls cannot be avoided, refer to the Citrix whitepaper CTX101810

– Communication Ports Used By Citrix Technologies, for the list of ports that should be enabled for

full functionality.

Growth

As the farm grows, administrators will need to decide whether to add more resources to the

provisioning servers or to add more provisioning servers to the farm.

There are a number of environmental factors that need to be considered when determining

whether the Provisioning Servers should be scaled up or scaled out:

 Redundancy – Spreading user load across additional less-powerful servers helps reduce

the number of users affected from a single provisioning server failure. If the business is

unable to accept the loss of a single high-specification server, consider scaling out.

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 Failover times – The more target devices connected to a single provisioning server, the

longer it will take for them to failover in the event that the server fails. Consider scaling

out to reduce the time required for target devices to failover to another server.

 Data center capacity – The data center may have limited space, power and/or cooling

available. In this situation, consider scaling up.

 Hardware costs – Initially, it may be more cost effective to scale up. However, there will

be a point where scaling out actually becomes more cost effective. A cost analysis

should be performed to make that determination.

 Hosting costs – There may be hosting and/or maintenance costs based on the number

of physical servers used. If so, consider scaling up to reduce the long-term cost of these

overheads.

Decision: Network Configuration

As mentioned before it is essential that the network is sized correctly to prevent network

bottlenecks causing high disk access times and directly affecting virtual desktop performance.

The following diagram outlines a common Provisioning Services network infrastructure:

Figure 33: Sample PVS Network Configuration

The following network configuration is recommended for the network sections outlined within

the diagram:

 PVS Uplink – All disk access from the target devices will be transferred via the PVS

network uplink. This means hundreds or even thousands of devices will use this network

connection. Therefore, it is vital that this connection is redundant and can failover

without any downtime. Furthermore, Citrix recommends a minimum bandwidth of

1Gbps per 500 target devices. For virtual provisioning servers a respective QoS quota or a

dedicated physical network uplink should be configured to ensure best performance.

 Hypervisor Uplink – Used by all PVS target devices hosted on a particular hypervisor host.

Therefore, redundancy with transparent failover is strongly recommended. Unless the

target devices run a very I/O intensive workload or perform I/O intensive tasks (e.g.

booting) simultaneously, a bandwidth of 1Gbps is sufficient for this uplink.

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 VM Uplink – All network traffic for a virtual machine, including PVS streaming traffic, will

traverse this virtual network connection. Unless the workload is extremely I/O intensive a

bandwidth of 100 Mbps is sufficient to handle even peak loads during I/O intensive

tasks, such as booting from vDisk. For example, a Windows 2012 R2 Server will read

approximately 232MB during a period of 90 seconds from the vDisk until the Windows

Logon Screen is shown. During this period an average data rate of 20.5 Mbps with peaks

up to 90 Mbps can be observed.

The following switch settings are recommended for Provisioning Services:

 Disable Spanning Tree or Enable PortFast – In a switching environment the Spanning

Tree Protocol (STP) places ports into a blocked state while it transmits Bridged Protocol

Data Units (BPDUs) and listens to ensure the BPDUs are not in a loopback configuration.

The port is not placed in a forwarding state until the network converges, which

depending on the size of the network, may incur enough time to cause Preboot

Execution Environment (PXE) timeouts. To eliminate this issue, disable STP on edge-

ports connected to clients or enable PortFast.

 Storm Control - Storm Control is a feature available on Cisco switches that allows a

threshold to be set whereby, multicast, broadcast, or unicast traffic may be suppressed.

Its purpose is to prevent malicious or erroneous senders from flooding a LAN and

affecting network performance. PVS Servers may send a large amount of traffic by

design that falls within a storm control threshold, therefore the feature should be

configured accordingly.

 Broadcast Helper – The broadcast helper is required to direct broadcasts from clients to

servers that would otherwise not be routed. In a PVS environment it is necessary to

forward PXE boot requests when clients are not on the same subnet as the servers. If

possible the recommended network design is to have PVS servers residing on the same

subnet as the target devices. This mitigates the risk of any service degradation due to

other networking infrastructure components.

The following network interface features should be taken into consideration when selecting a

network interface for Provisioning Services:

 TCP Offloading – Offloading I/O tasks to the network interface reduces CPU usage and

improves overall system performance, however, PVS Streaming Services can be

negatively impacted when Large Send Offload is enabled due to the extra work placed

on the network adapter. Many network adapters will have Large Send Offload and TCP

checksum offload enabled by default.

Note: If Large Send Offload is enabled and the switch that the traffic is passing through

does not support the frame size sent by the Large Send Offload engine, the switch will

drop the frame causing data retransmission. When retransmitting, the operating system

will segment the frames instead of the network adapter, which can lead to severe

performance degradation.

 Receive Side Scaling (RSS) – Receive side scaling enables packets received from a

network adapter to be balanced across multiple CPUs which allows incoming TCP

connections to be load balanced, preventing bottlenecks from occurring to a single CPU.

In Windows Server 2008 R2 and Windows Server 2012/2012 R2, RSS is enabled by

default.

Note: For more information on PVS networking best practices please refer to Best Practices for

Configuring Provisioning Services Server on a Network.

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Note: For Provisioning Services implementations on low bandwidth networks (1Gbps or slower),

performance may be improved by isolating streaming traffic from other network traffic on the

LAN.

Note: Microsoft does not support NIC teaming with Hyper-V on Windows Server 2008 R2;

however, third party solutions are available. Microsoft does support NIC teaming with Hyper-V on

Windows Server 2012/2012 R2. All support queries regarding teaming with Hyper-V should be

directed to the NIC OEM.

Decision: Subnet Affinity

The Provisioning Services Subnet Affinity is a load balancing algorithm that helps to ensure

target devices are connected to the most appropriate provisioning server. When configuring

subnet affinity, the following options are available:

 None – Ignore subnets; uses the least busy server.

 Best Effort – Uses the least busy server/NIC combination from within the same subnet. If

no server/NIC combination is available within the subnet, select the least busy server

from outside the subnet. If more than one server is available within the selected subnet,

perform load balancing between those servers. This is the default setting.

 Fixed – Use the least busy server/NIC combination from within the same subnet. Perform

load balancing between servers within that subnet. If no server/NIC combination exists

in the same subnet, do not boot target devices assigned to this vDisk.

The following examples show common network configurations for physical provisioning servers.

Similar configurations can be implemented for virtual provisioning servers without

compromising on performance or functionality.

Blade Design

The provisioning servers and the target devices that they support reside within the same chassis.

In most cases, the chassis will have a dedicated 10Gbps switch shared among all blade servers

within the chassis.

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Figure 34: PVS Blade Enclosure Design

The “Best Effort” subnet affinity option is used to keep Provisioning Services traffic within the

same chassis. Should the provisioning server become unavailable, the targets will failover to the

second provisioning server in the second chassis, but same Provisioning Services site.

Rack Design

The second example is based on a rack design that uses rack switches to keep the provisioning

traffic within the rack.

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Server Rack

Rack Switch

Provisioning Services

XenServer

IP Subnet

Server Rack

Provisioning Services

XenServer

IP Subnet

Core Switch

Rack Switch

PVS Site

Figure 35: PVS Rack Design

As opposed to the blade chassis design, the subnet affinity feature is not used. Instead a

Provisioning Services site with two provisioning servers will be configured per server rack. This will

ensure that the target devices are streamed from provisioning servers within the same rack.

Decision: Read Cache

PVS Accelerator enables a PVS proxy to reside in the XenServer's Control Domain on a host

where streaming of a Provisioning Services vDisk is cached at the proxy before being forwarded

to the virtual machine. Using the cache, subsequent booting (or any I/O requests) of the virtual

machine on the same host can be streamed from the proxy rather than streaming from the

Experience from the Field

Manufacturing – A manufacturing company is designing a Provisioning Services solution

to support five thousand virtual desktops. The company has concerns that Provisioning

Services streaming traffic will create a bottleneck on the network affecting other

applications. The company chose to build the environment on blade servers so that

provisioning traffic is contained within the blade enclosure and will not impact other

traffic on the network.

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server over the network. PVS Accelerator requires more local resources on the XenServer host,

but streaming from the server over the network saves resources, effectively improving

performance.

Table 48: PVS Read Cache (PVS Accelerator)

PVS Accelerator is a XenServer only capability. Utilizing this integrated technology reduces the

load on the PVS server, reduces the overall network utilization and reduces the time it takes to

boot a virtual machine.

For more information on the relationship among XenServer and Provisioning Services, see the

blog XenServer and PVS: Better Together.

Decision: Write Cache

Because the master image is read-only, each virtual machine has a writable disk to store all

changes. The administrator must decide where to store the write cache disk.

Citrix XenServer

Shared Storage

Write Cache

Master Image

Write Cache

Virtual Desktop/App

PVS Server

PVS Accelerator

100

PVS CPU Utilization Network Throughput Average VM Boot Time

Percent

PVS Accelerator - Percent Resource Reduction

Provisioning Services Provisioning Services Accelerator

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PVS Server – Local Storage

The Provisioning Services local storage holds the write cache drives for each target virtual

machine. Although this is the default setting, it does increase network bandwidth requirements

and increases the utilization of the Provisioning Services server.

Figure 36: Server-side Local Storage Write Cache

PVS Server – Shared Storage

Shared storage associated with the Provisioning Services server holds the write cache drives for

each target virtual machine. This option does increase network bandwidth requirements and

increases the utilization of the Provisioning Services server. It also places temporary data (write

cache) on expensive shared storage.

Figure 37: Server-side Shared Storage Write Cache

VM – Local Storage

Local storage associated with the virtual machine holds the write cache drives for each target

virtual machine. This option uses low cost local storage and does not consume additional

resources on the Provisioning Services server. However, the local storage must be capable of

support the IOPS of all virtual machines on the host.

Citrix XenServer, Microsoft Hyper-V, VMware vSphere

Write Cache

Master Image

Write Cache

Virtual Desktop/App

PVS Server

Shared Storage

Citrix XenServer, Microsoft Hyper-V, VMware vSphere

Write Cache

Master Image

Write Cache

Virtual Desktop/App

PVS Server

Shared Storage

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Figure 38: VM Local Storage Write Cache

VM – Cache in RAM

RAM associated with the virtual machine holds the write cache drives for each target virtual

machine. This option provides high performance due to the speed of RAM. However, if the RAM

cache runs out of space, the virtual machine will become unusable. In order to use this option,

significant amounts of RAM must be allocated to each virtual machine, increasing the overall

cost.

Figure 39: VM Cache in RAM

VM – Cache in RAM with Overflow to Disk

A combination of RAM and local storage is used for the write cache. First, writes are stored within

the RAM cache, providing high performance. As the RAM cache is consumed, large blocks are

removed from the RAM cache and placed onto the local storage write cache disk. This option

provides high-levels of performance with the low cost of local storage.

Citrix XenServer, Microsoft Hyper-V, VMware vSphere

Write Cache

Master Image

Write Cache

Virtual Desktop/App

PVS Server

Shared Storage

Citrix XenServer, Microsoft Hyper-V, VMware vSphere

Shared Storage

Master Image

Virtual Desktop/App

PVS Server

RAM-Based

Write Cache

RAM-Based

Write Cache

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Figure 40: VM Cache in RAM

Utilizing this integrated technology reduces write IOPS by 95%.

Cache in RAM with Overflow to Disk is the recommended option.

Decision: Antivirus

By default, most antivirus products scan all files and processes, which has a significant impact on

Provisioning Services performance. For details on how antivirus software can be optimized for

Provisioning Services, please refer to CTX124185 – Provisioning Services Antivirus Best Practices.

Antivirus software can cause file-locking issues on provisioning servers. The vDisk Store and write

cache should be excluded from antivirus scans in order to prevent file contention issues.

When a virtual disk is running in standard mode and needs to be restarted, it downloads all of

the previously loaded virus definitions. This can cause performance degradation when restarting

several target devices at a time, often causing network congestion while the operation persists.

In extreme cases, the target device and provisioning server can become sluggish and consume

Citrix XenServer, Microsoft Hyper-V, VMware vSphere

Shared Storage

Write Cache

Master Image

Write Cache

Virtual Desktop/App

PVS Server

RAM-Based

Write Cache

RAM-Based

Write Cache

Windows 2012R2 Windows 10

Average IOPS

Steady State Write IOPS - Provisioning Services

Without MCS RAM Cache With MCS RAM Cache

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more resources than necessary. If the antivirus software supports it, definition files should be

redirected to the write cache drive so that they are preserved between reboots.

Machine Creation Services

Machine Creation Services (MCS) uses disk-cloning technology to simplify the deployment of virtual

machines. Computers are provisioned and re-provisioned in real-time from a single shared-disk

image. In doing so, administrators can eliminate the need to manage and patch individual systems.

Instead, administrators perform all image management on the master image.

Decision: Storage Location

Machine Creation Services allows administrators to break up a virtual desktop into multiple

components and store those pieces on different storage arrays.

Shared Storage

The first option utilizes shared storage for the operating system disk and the differencing disk.

Table 49: MCS Shared Storage

Although this option allows the sharing of the master image across multiple hypervisor hosts, it

puts more strain on the storage array because it must also host the differencing disk, which is

temporary data.

Hybrid Storage

The second option uses shared storage for the operating system disk and local hypervisor

storage for the differencing disk.

Citrix XenServer, Microsoft Hyper-V, VMware vSphere

Shared Storage

Identity Disk

Differencing Disk

Master Image

Identity Disk

Differencing Disk

Virtual Desktop/App

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Table 50: MCS Hybrid Storage

This is the most common option giving the administrator the benefits of sharing of the master

image across multiple hypervisor hosts while offloading expensive, temporary write IOPS to

cheap, local hypervisor storage.

XenServer IntelliCache Storage

The third option uses shared storage for the operating system disk and local hypervisor storage

for the differencing disk and local XenServer storage for a local cache of the operating system

disk.

Table 51: MCS IntelliCache

This is only an option for XenServer implementations. It provides the same value as the hybrid

storage approach while also reducing read IOPS from shared storage. IntelliCache can coexist

with the XenServer RAM-based read cache, if XenServer RAM is limited.

Decision: Cloning Type

Machine Creation Services incorporates two types of cloning techniques.

 Thin - Every VM within the catalog utilizes a single, read-only virtual disk for all reads. A

second virtual disk, unique for each VM, captures all write IO activity.

Citrix XenServer, Microsoft Hyper-V, VMware vSphere

Shared Storage

Identity Disk

Differencing Disk

Master Image

Identity Disk

Differencing Disk

Virtual Desktop/App

Citrix XenServer

Shared Storage

Identity Disk

Differencing Disk

Master Image

Identity Disk

Differencing Disk

Virtual Desktop/App

Intellicache

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 Full – Every VM within the catalog receives a full copy of the master disk image. Each VM

fully owns the disk, allowing for read/write activity. Full cloning technology is only

available for personal virtual desktops, where a dedicated virtual machine saves all

changes to a local disk.

Administrators should consider the following when deciding between thin and full cloning

technologies:

Thin Clone

Full Clone

Storage Space

Requirements

Has greatest storage space savings.

A single master disk image is shared

across multiple VMs. Only the

differencing disk (writes) consume space,

which continues to grow until the VM

reboots

High storage space requirements

Each VM receives a full copy of the

master image. The size continues to

grow as changes are made to the VM.

Backup /

Restore

Difficult

Many 3rd party Backup/DR solutions do

not support snapshot/delta disks,

making thin provisioned VMs

hard/impossible to backup or move to

other storage arrays.

Easy

The VM exists within a single virtual disk,

making it easy to backup and restore.

Provisioning

Speed

Fast

Only requires a single disk image

Slow (can be mitigated)

Each VM requires a full copy of the

master image. Storage optimization

technologies can help mitigate.

Performance

Slower

A read I/O can occur twice, one for

master disk and one for differencing

disk, increasing read IOPS.

Faster

All read/write direct to a single disk.

Boot Storm

High Impact

In a boot storm, all differencing disks re-

size to hold all writes from Windows

start up; placing a high load on the

storage as it happens all at once.

Low Impact

Table 52: Machine Creation Services Thin/Full Cloning

Decision: Read Cache

During boot and logon, virtual desktops incur high levels of storage read IOPS, which can put a

strain on the underlying storage subsystem. When deployed on Citrix XenServer, Shared and

Pooled VDI modes utilize a RAM-based read cache hosted on each XenServer.

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Table 53: MCS Read Cache

Utilizing this integrated technology reduces read IOPS by 50-80%.

Decision: Write Cache

During steady state, virtual desktops incur high levels of storage write IOPS, which can put a

strain on the underlying storage subsystem. Shared and Pooled VDI modes can utilize a RAM-

based write cache by using non-paged pool RAM from the virtual machines operating system.

Citrix XenServer

Shared Storage

Identity Disk

Differencing Disk

Master Image

Identity Disk

Differencing Disk

Virtual Desktop/App

RAM-Based

Read Cache

Windows 2012R2 Windows 10

Average IOPS

Boot Read IOPS - Machine Creation Services

Without XenServer Read Cache With XenServer Read Cache

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Table 54: MCS Write Cache

Utilizing this integrated technology reduces write IOPS by 95%.

Security

Depending on the requirements of the organization, different security standards should be

implemented within the solution. It is advisable refer to the following papers:

 Getting Started Guide for Security

 End-to-End Encryption

 System Hardening Guide

 Common Criteria

 Secure Browsing

Citrix XenServer, Microsoft Hyper-V, VMware vSphere

Shared Storage

Identity Disk

Differencing Disk

Master Image

Identity Disk

Differencing Disk

Virtual Desktop/App

RAM-Based

Write Cache

RAM-Based

Write Cache

Windows 2012R2 Windows 10

Average IOPS

Steady State Read IOPS - Machine Creation Services

Without MCS RAM Cache With MCS RAM Cache

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Layer 5: The Hardware Layer

Hardware Sizing

This section covers hardware sizing for the virtual infrastructure servers, virtual desktops, and virtual

application hosts. The sizing of these servers is typically done in two ways.

 The first and preferred way is to plan ahead and purchase hardware based on the workload

requirements.

 The second way is to use existing hardware in the best configuration to support the different

workload requirements.

This section will discuss decisions related to both methods.

Decision: Workload Separation

When implementing a XenApp and XenDesktop deployment, the workloads for the infrastructure,

XenDesktop, and XenApp workloads can be separated into dedicated resource clusters or mixed on

the same physical hosts. Citrix recommends using resource clusters to separate the workloads,

especially in an enterprise deployment. This allows better host sizing as each workload has unique

requirements such as overcommit ratios and memory usage.

In smaller environments where resource clusters are cost prohibitive, the workloads may be mixed in

a manner which still allows for a highly available environment. Citrix leading practice is to separate

the workloads however mixed workloads is a cost based business decision.

Decision: Physical Processor (pCPU)

The following table provides guidance on the number of virtual desktops that can be supported

for light, medium and heavy workloads per physical core. Each desktop correlates to a single

concurrent user, with the assumption that the operating system underwent optimization.

User

Workload

Operating System

Users per Physical Core

Light

Windows 7

Windows 8

Windows 10

Windows 2008R2

Windows 2012R2

Windows 2016

Medium

Windows 7

Windows 8

Windows 10

Windows 2008R2

Windows 2012R2

Windows 2016

Heavy

Windows 7

Windows 8

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Windows 10

Windows 2008R2

Windows 2012R2

Windows 2016

Table 55: Processor Requirements by Workload

The estimate for “Users per Physical Core” is a baseline number running Microsoft Office 2010.

The baseline number must be adjusted based on specific infrastructure requirements. As a

general guideline, the following characteristics are baseline changes to server density.

Characteristic

Server Density Impact

Antivirus (not optimized)

25% decrease

Real-time Monitoring

15% decrease

Office 2013

20% decrease

Office 2016

25% decrease

Hyper-Threading

20% increase

Table 56: Server Density Adjustments

To estimate the total number of physical cores required for the XenApp and XenDesktop

workload, use the following formula for each user group:

  









  



        





  









  



        





∑ represents the sum of all user group combinations “i”.

Users

= Number of concurrent users per user groups

UsersPerCore

= Number of users per physical core

AV = Antivirus impact (default = 0.25)

Mon = Monitoring tools impact (default = 0.15)

Off13 = Office 2013 impact (default = .2)

Off16 = Office 2016 impact (default = .25)

HT = Hyper-Threading impact (default = .2)

If workloads will be separated (XenApp and XenDesktop workloads), the formula should be

calculated twice, once for all XenDesktop users and the second for all XenApp users in order

Decision: Physical Memory (pRAM)

The recommended method for sizing memory to a physical host is to size based on the total

memory required to support the virtual machines and the CPU capacity of the host. In order to

calculate the total memory required for XenApp and XenDesktop, simply multiply the number of

virtual machines by the amount of memory allocated to the virtual machines. The sum of all of

the machine catalogs will be the total RAM required for XenApp and XenDesktop hosts. This is

shown in the formula below.

  











Citrix VDI Handbook - XenApp and XenDesktop 7.15 LTSR

Page 133

  











∑ represents the sum of all user group combinations “i”.

= Number of concurrent users per user groups

vRAM

= Amount of RAM assigned to each virtual machine

If workloads will be separated onto different hosts (XenApp and XenDesktop workloads), the

formula should be calculated twice, once for all XenDesktop users and the second for all XenApp

users.

Decision: Physical Host (pHost)

In most situations, the number of physical hosts (pHost) to support the XenApp and XenDesktop

workloads will be limited on the number of processor cores available.

The following formula provides an estimate for the number of hosts required for the user

workloads. The formula is based on the best practice of separating the XenApp and XenDesktop

workloads due to the different recommended CPU overcommit ratios for each.

  





 

  





 

Once the number of physical hosts has been determined based on processor cores, the amount

of RAM for each host is calculated.

   



  



   



  



Decision: GPU

Hosts used to deliver graphical workloads require graphics processors to deliver a high end user

experience. Specific hardware hosts and graphics cards are required to support high end graphics

using HDX 3D Pro. An updated list of tested hardware is available in a knowledge base article. Sizing

of the desktop and application hosts of high end graphics users should be based on the GPU

requirements ensuring that the host then has adequate CPU and memory resource to support the

workload.

NVIDIA GRID cards can be leveraged with vGPU profiles to support multiple users. Sizing guidelines

are provided from NVIDIA in the table below.

NVIDIA

GRID

Graphics

Board

Virtual

GPU

Profile

Application

Certifications

Graphics

Memory

Max

Displays

Per

User

Max

Resolution

Per

Display

Max

vGPU

Per

Graphics

Board

Use Case

GRID K2

K280Q

4,096

2560x1600

Designer

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K260Q

2,048

2560x1600

Designer/Power

User

K240Q

1,024

2560x1600

Designer/Power

User

K220Q

512 MB

2560x1600

Designer/Power

User

K200

256 MB

1900x1200

Knowledge

Worker

GRID K1

K180Q

4,096

2560x1600

Power User

K160Q

2,048

2560x1600

Power User

K140Q

1,024

2560x1600

Power User

K120Q

512 MB

2560x1600

Power User

K100

256 MB

1900x1200

Knowledge

Worker

Storage Sizing

Decision: Storage Architecture

The primary storage architectures are as follows:

 Local Storage - Uses hard disks directly attached to the computer system. The disks

cannot be shared with other computer systems, but if the computer is hosting pooled or

hosted shared desktops, a shared storage solution is not necessary. In many cases local

storage can perform as well as shared storage. Scalability is limited to the number of

drive bays available in the computer system. Many blade servers for example have just

two drive bays, so using local storage to support a XenDesktop deployment may not be

optimal.

 DAS - Storage sub-system directly attached to a server or workstation using a cable. It

uses block-level storage and can be a hard disk local to the computer system or a disk

shelf with multiple disks attached by means of external cabling. Unlike local disks, disk

shelves require separate management. Storage shelves can be connected to multiple

servers so the data or disks can be shared.

 NAS - Provides file-level storage to computer systems through network file shares. The

NAS operates as a file server, and NAS systems are networked appliances which contain

one or more hard drives, often arranged into logical, redundant storage containers or

RAID arrays. Access is typically provided using standard Ethernet and network file sharing

protocols such as NFS, SMB/CIFS, or AFP.

Note: NAS can become a single point of failure. If the network share becomes

unavailable, all target devices streamed from the disk will be unavailable as well.

 SAN - Dedicated storage network that provides access to consolidated, block-level

storage. SANs allow computers to connect to different storage devices, so no server has

ownership of the storage subsystem enabling data to be shared among multiple

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computers. A SAN will typically have its own dedicated network of storage devices that

are generally not accessible through the network by standard means. In order to

connect a device to the SAN network a specialized adapter called the Host Bus Adapter

(HBA) is required. SANs are highly scalable with no noticeable change in performance as

more storage and devices are connected. SANs can be a costly investment both in terms

of capital and the time required to learn, deploy and manage the technology.

 Hybrid - A NAS head refers to a NAS which does not have any on-board storage, but

instead connects to a SAN. In effect, it acts as a translator between the file-level NAS

protocols (NFS, CIFS, etc.) and the block-level SAN protocols (Fibre Channel and iSCSI).

Thus it can combine the advantages of both technologies and allows computers without

Host Bus Adapters (HBA) to connect to centralized storage.

The following table summarizes the storage options available and rates their suitability for

XenDesktop deployments.

Storage Properties

Local

DAS

NAS

SAN

Implementation

costs

Low

Medium

High

Administration

Low

Medium

High

Performance

High

Med - High

High

Redundancy

Low - Med

Medium

Med – High

High

Scalability

Low

Low - Med

Med - High

High

Typical use case

Small to

medium

production and

test

environments

Small to

medium

production

environments.

Small to medium

production

environments.

Medium to large

production

environments.

Table 57: Storage feature comparison

Note: Hyper-V 2008 R2 does not support NAS technology. Hyper-V 2012/2012 R2 only supports

NAS solutions that support the SMB 3.0 protocol. For more information please refer to the Hyper-

V 2008 R2 and Hyper-V 2012 R2 sections of the handbook.

Local storage is best suited for storing virtual machines which do not have high availability

requirements or persistent data attached such as random (pooled) desktops or hosted shared

desktops. Local and DAS is suited for storing user data and home directory files. If using Machine

Creation Services, master images as well as any updates must be replicated to each server.

NAS and SAN storage is best suited for infrastructure servers supporting the XenDesktop

environment, and virtual machines with persistent data such as static (dedicated) desktops.

Decision: RAID Level

To choose the optimal RAID level, it is necessary to consider the IOPS and read/write ratio

generated by a given application or workload in combination with the individual capabilities of a

RAID level. For hosting read intensive workloads, such as the Provisioning Services vDisk store,

RAID levels that are optimized for read operations such as RAID 1, 5, 6, 10 are optimal. This is

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because these RAID levels allow read operations to be spread across all disks within the RAID set

simultaneously.

For hosting write intensive workloads, such as Provisioning Services write cache and Machine

Creation Services differencing disks, RAID levels such as RAID 1 or 10 are optimal, as these are

optimized for writes and have a low write penalty.

The following table outlines the key quantitative attributes of the most commonly used RAID

levels:

RAID

Capacity

Fault Tolerance

Read

Performance

Write Performance

Minimum #

of Disks

100%

None

Very High

High

(Write Penalty 1)

50%

Single-drive failure

Very High

Medium

(Write Penalty 2)

67%-94%

Single-drive failure

High

Low

(Write Penalty 4)

50%-88%

Dual-drive failure

High

Low

(Write Penalty 6)

50%

Single-drive failure

in each sub array

Very High

Medium

(Write Penalty 2)

Table 58: RAID levels

Note: The write penalty is inherent in RAID data protection techniques, which require multiple disk

I/O requests for each application write request, and ranges from minimal (mirrored arrays) to

substantial (RAID levels 5 and 6).

Decision: Number of Disks

To determine the number of disks required it is important to understand the performance

characteristics of each disk, the characteristics of the RAID level and the performance

requirements of the given workload. The basic calculation for determining the total number of

disks needed is:

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 



  







For example, a disk manufacturer is reporting that a particular disk array which they have

developed has a total workload IOPS of 2000. The raw IOPS per disk is 175. To determine how

many disks are required to support a workload with 20% read operations and 80% write

operations on RAID 10:

 





  







  



 



 

Based on the previous example, the following table shows how the disk count will vary based on

the RAID level and the read/write ratio.

RAID

RAW IOPS

(per disk)

Workload IOPS

Read %

Write %

Disk count

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175

2000

20%

80%

175

2000

80%

20%

1 / 10

175

2000

20%

80%

175

2000

80%

20%

175

2000

20%

80%

175

2000

80%

20%

Table 59: Example of how disk count changes per RAID level and R/W ratio

Decision: Disk Type

Hard disk drives (HDDs) are the traditional variation of disk drives. These kinds of disks consist of

rotating platters on a motor-driven spindle within a protective enclosure. The data is

magnetically written to and read from the platter by read/write heads.

Different implementations of this technology are available on the market, which differ in terms

of performance, cost and reliability.

 Serial ATA (SATA) disk transmit data serially over two pairs of conductors. One pair is for

differential transmission of data, and the other pair is for differential receiving of data.

SATA drives are widely found in consumer desktop and laptop computers. Typical SATA

drives have transfer speeds ranging from 1500 – 6000Mbps and support hot-swapping

by design.

 Small Computer Systems Interface (SCSI) disks use a buffered, peer to peer interface that

uses handshake signals between devices. Many SCSI devices require a SCSI initiator to

initiate SCSI transactions between the host and SCSI target. SCSI disks are common in

workstations and servers and have throughputs ranging from 40 – 5120Mbps. iSCSI

(Internet Small Computer System Interface) is a mapping of the regular SCSI protocol

over TCP/IP, more commonly over Gigabit Ethernet.

 Fibre Channel (FC) disk is the successor to the parallel SCSI disk and is common in SAN

storage devices. Fibre Channel signals can run on an electrical interface or fibre-optic

cables. Throughput can range from 1 – 20Gbps, and connections are hot-pluggable.

 Serial Attached SCSI (SAS) disk uses a new generation serial communication protocol to

allow for higher speed data transfers than SATA disks. Throughput can range from 2400

– 9600Mbps.

In contrast to traditional hard disks, Solid State Disks (SSDs) use microchips to retain data in

either NAND non-volatile memory chips (flash) or DRAM and contain no moving parts. SSDs are

less susceptible to physical shock, have lower access times and latency and have higher I/O rates.

SSDs have significantly higher random read performance. An SSD drive can attain anywhere from

5,000 to 20,000 random reads per second. SSDs are also more expensive per gigabyte (GB) and

typically support a limited number of writes over the life of the disk.

Flash memory-based SSDs can be either based on multi-level cells (MLC) or single-level cells

(SLC). SLC devices only store one bit of information in each cell. MLC devices can store multiple

bits of information with each cell. Flash based SSDs cost lower than DRAM based SSDs but

perform slower. DRAM based SSD devices are used primarily to accelerate applications that

would otherwise be held back by the latency of flash SSDs or traditional HDDs.

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SSDs were previously not viable for enterprise storage solutions because of the high cost, low

capacity and fast wear of the drives. Improvements in SSD technology and lowering costs are

making them more favorable over HDDs. Solid state hybrid drives (SSHD) combine the features

of SSDs and HDDs, by containing a large HDD drive with an SSD cache to improve performance

of frequently accessed data.

Comparing SSDs and HDDs is difficult since HDD benchmarks are focused on finding the

performance aspects such as rotational latency time and seek time. As SSDs do not spin, or seek,

they may show huge superiority in such tests. However, SSDs have challenges with mixed reads

and writes and their performance may degrade over time.

The following table compares the transfer rates of some of the more common storage types

available on the market today.

Technology

Rate (bit/s)

iSCSI over Fast Ethernet

100Mbps

Ultra-2 wide SCSI (16

bits/40 MHz)

640Mbps

iSCSI over Gigabit Ethernet

1,000Mbps

SATA rev 3

6,000Mbps

SAS 3

9,600Mbps

FCoE over 10GbE

10,000Mbps

SATA rev 3.2 – SATA Express

16,000Mbps

iSCSI over Infiniband

32,000Mbps

Table 60: Common disk types and transfer rates

SCSI and SATA disks are best suited for storing data that does not have high performance

requirements like the PVS vDisk store. SAS, Fibre Channel, or SSD drives are best suited for storing

data that have high performance requirements like the PVS write cache.

Decision: Storage Bandwidth

Storage bandwidth is the connectivity between servers and the storage subsystem.

Understanding bandwidth requirements can help determine the proper hardware for delivering

data and applications at speeds for a positive end user experience. For most datacenters 10Gbps

Ethernet or 10Gbps FCoE is sufficient for storage connections. Smaller environments however

may only need 1Gbps bandwidth. In virtualized environments it is not just important to look at

the bandwidth requirements of the physical host and storage subsystem, but determining how

much bandwidth is required for each virtual machine plays a factor too.

In order to plan for the required bandwidth, it is necessary to determine the throughputs for

every individual system that uses a shared component or network path. For example, the

following information is provided for an environment with 100 similar virtual machines (hosted

on 10 virtualization hosts and connected to one NAS head).

Average

Peak

Throughput per VM

10Mbps

30Mbps

Throughput per host

100Mbps

(10 VMs * 10Mbps)

300Mbps

(10 VMs * 30Mbps)

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Throughput per storage

1Gbps

(10 hosts * 100Mbps)

3Gbps

(10 hosts * 300Mbps)

Table 61: Throughput

The NIC used for storage communication needs to be a 1Gbps adapter in order to handle the

peak load. The NAS head as well as its network connection need to support 3Gbps worth of data

traffic in order to support the peak load of all systems.

Decision: Tiered Storage

A one-size-fits-all storage solution is unlikely to meet the requirements of most virtual desktop

implementations. The use of storage tiers provides an effective mechanism for offering a range

of different storage options differentiated by performance, scalability, redundancy and cost. In

this way, different virtual workloads with similar storage requirements can be grouped together

and a similar cost model applied.

For example, a XenDesktop implementation using tiered storage may look like the following:

 Tier 1 storage group - Write intensive files such as the write cache and differencing disks

are placed in a storage group consisting of SSDs.

 Tier 2 storage group - Mission critical data, or data that requires high availability, are

placed in a storage group consisting of less expensive high performing drives.

 Tier 3 storage group - Seldom used data files, read-only files, or other non-mission

critical data placed in a storage group consisting of low cost and lower performing

drives.

Decision: Thin Provisioning

Thin provisioning allows more storage space to be presented to the virtual machines than is

actually available on the storage repository. This lowers storage costs by allowing virtual

machines access to disk space that is often unused. This is particularly beneficial to Machine

Creation Services which uses a linked-clone approach to provisioning virtual machines. Thin

provisioning minimizes the storage space required for the master image copies used to build

virtual machines. Thin provisioning is possible at the physical storage layer, a feature usually

available with most SAN solutions, and at the virtual layer. NFS based storage solutions will

usually have thin provisioning enabled by default.

At the physical storage layer, it is important to ensure that sufficient storage is available to

prevent the risk of virtual machines not being available in a storage “overcommit” scenario when

available disk space is exhausted. Organizations should decide if the cost savings thin

provisioning provides outweighs the associated risk and consider enabling if the storage solution

supports it.

Note: Virtual machines may not function if disk space is exhausted so it is important to have a

process in place, either through alerts or notifications that will give administrators enough time to

add more disks to the storage solution so that the XenDesktop environment is not impacted.

Decision: Data De-Duplication

Data de-duplication is a data compression technique whereby duplicate data is replaced with

pointers to a single copy of the original item. This reduces storage requirements and costs by

improving storage utilization, however it can impact storage performance. There are two

implementations of de-duplication available:

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 Post-process de-duplication – The de-duplication is performed after the data has been

written to disk. Post-process de-duplication should be scheduled outside business hours

to ensure that it does not impact system performance. Post Process de-duplication

offers minimal advantages for random desktops as the write-cache/difference disk is

typically reset on a daily basis.

 In-line de-duplication – Examines data before it is written to disk so that duplicate blocks

are not stored. The additional checks performed before the data is written to disk can

sometimes cause slow performance. If enabled, in-line duplication should be carefully

monitored to ensure that it is not affecting the performance of the XenDesktop

environment.

If the storage solution supports it, enabling post-process data de-duplication is recommended

for minimal impact to XenDesktop performance.

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Section 4: Monitor

Overview

Like any integrated system, monitoring and maintenance is critical to the overall health of the solution.

Without proper support, operations and health monitoring systems in place, the user experience will

slowly start to degrade.

Process 1: Support

When problems arise, technical support is the first point of contact. This section addresses the proper

staffing, organization, training, delegated administration and tools that should be used to maintain the

Citrix deployment.

Decision: Support Structure

Multiple levels of support have been found to be the most effective ways of addressing support

issues. Low criticality, low complexity or frequently occurring issues should be managed and

resolved at the lower support levels. High criticality and complex issues are escalated to more

experienced architects or infrastructure owners. The diagram below outlines a common multi-level

support structure.

Figure 41: Support Structure

If a user encounters an issue, Level-1 support (help desk) is the entry point to the support system.

Level-1 should resolve 75% of all issues encountered, of which a majority will be routine problems

that only require a limited knowledge of the Citrix environment. At this level, issues are quickly

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resolved and some may be automated (self-service), for example password resets and resource

provisioning.

Non-routine problems that exceed Level-1’s abilities are escalated to Level-2 (Operators). This

support level is generally comprised of administrators supporting the production Citrix environment.

Information on the end user’s problem and attempted troubleshooting steps are documented at

the first level allowing Level-2 technicians to immediately begin addressing the problem. Level-2

technicians should handle only 20% of the support tickets and are highly knowledgeable on the

Citrix environment.

Complex issues that exceed Level-2’s abilities should be escalated to Level-3 (Implementers). Level-2

and Level-3 support may often both be members of the Citrix Support Team, with Level-3

comprising the senior staff maintaining the Citrix environment. Level-3 issues are complicated and

often mission critical requiring expert knowledge of the virtual desktop and application

environment. Level-3 support tickets should amount to no more than 5% of all support issues.

The final level, Level-4 (Architects), is focused on the strategic improvements for the solution, testing

new technologies, planning migrations, and other high level changes. Generally, Level-4 is not

involved in active support of a production environment.

Should support discover an issue that is related to an application or underlying infrastructure, the

ticket is handed to the appropriate team for troubleshooting. If a program bug is discovered, the

issue is then re-escalated and a ticket is established with the appropriate vendor.

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Decision: Support Responsibilities and Skill Set

The following table highlights the recommended characteristics of each support level.

Support Level

Description

Responsibilities

Skill Set

Level-1

(Help Desk)

Provide first-line support

of reported issues.

Initially, servicing support

messages and phone

calls. This level needs to

perform initial issue

analysis, problem

definition, ticket routing,

and simple issue

resolution. Often

processes requests for

application access or

support with configuring

plugins.

 Perform issue definition, initial analysis and basic

issue resolution

 Perform initial troubleshooting to determine the

nature of the issue

 Create ticket, collect user information, and log all

troubleshooting steps performed

 Resolve basic Citrix related issues, connectivity

problems and application related issues using

existing knowledge base articles

 Escalate issue to Level-2 if advanced skills or

elevated permissions are required

 Ability to isolate the issue to be Citrix related,

Microsoft related or third party Application related

 If it affects the production environment or is

potentially causing a system level outage, escalate

directly to Level-3

 Generate requests for additional issue resolution

guides as necessary

 Follow up with end users when a support ticket is

closed to ensure the problem has been

satisfactorily resolved

 General Citrix XenApp/XenDesktop knowledge

(CCA, CCA-V)

 General Windows client OS/server OS knowledge

(MCP)

 General Active Directory knowledge

 General Networking knowledge (CCNA)

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Level-2

(Operators)

Primarily supporting day-

to-day operations of the

Citrix environment; may

include proactive

monitoring and

management. In

addition, this role should

also perform

intermediate level

troubleshooting and

utilize available

monitoring or

troubleshooting tools.

Assist with resolving

issues escalated by Level-

1 support.

 Perform intermediate issue analysis and resolution.

 Identify root cause of issues.

 Respond to server alerts and system outages.

 Create weekly report on number of issues, close

rate, open issues, etc.

 Review vendor knowledge base articles.

 Respond to out-of-hours helpdesk calls.

 Respond to critical monitoring alerts.

 Generate internal knowledge base articles and

issue resolution scripts and maintain Level-1

troubleshooting workflows.

 Perform basic server maintenance and operational

procedures.

 Manage user profiles and data.

 Escalate ticket to Level-3 or appropriate

technology owner if advanced skills or elevated

permissions are required.

 Generate requests for additional issue resolution

scripts and knowledge base articles as necessary.

 Able to read built-in event logs for Windows and

Citrix to do basic troubleshooting following public

information via Google/Bing.

 Experience with Microsoft Windows Server

including but not limited to:

o Configuring operating system options

o Understanding Remote Desktop Services

policies and profiles

o Using Active Directory

o Creating users/managing permissions and

administrator rights

o Creating and modifying Active Directory

group policies

 Basic administration skills, including:

o An understanding of protocols (TCP)

o An understanding of firewall concepts

o An understanding of email administration and

account creation

o An understanding of Remote Desktop

Services policies and profiles

o The ability to create shares and give access to

shared folders/files

 Experience performing the following:

o Managing, maintaining, monitoring and

troubleshooting Citrix solutions

o Backing up components in Citrix

environments

o Updating components in Citrix environments

o Creating reports for trend analysis

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Level-3

(Implementer)

Central point for

implementing,

administering and

maintaining Citrix

desktop and application

virtualization

infrastructure. This role

focuses on deploying

new use cases and

leading lifecycle

management initiatives.

Generally, one

Implementer could focus

on one use-case at a

time. For example, three

new concurrent use

cases would require

three Implementers.

Escalates issues to

software vendor specific

technical support and

notifies Level-4 about

this issue.

 Perform advanced issue analysis and resolution.

 Perform maintenance and environment upgrades.

 Addresses high severity issues and service outages.

 Manage the Citrix environment.

 Oversee and lead administrative tasks performed

by Level-2.

 Manage network and storage infrastructure as it

relates to the Citrix environment (depending on

size of company or Citrix environment).

 Review periodic reports of server health, resource

usage, user experience, and overall environment

performance.

 Review vendor knowledge base articles and newly

released updates.

 Perform policy-level changes and make Active

Directory updates.

 Review change control requests that impact the

Citrix environment.

 Perform advanced server and infrastructure

maintenance.

 Review knowledge base articles and issue

resolution scripts for accuracy, compliance, and

feasibility.

 Create knowledge base articles and issue

resolution scripts to address Level-2 requests.

 Escalate ticket to vendor specific technical support,

when necessary, and notify Level-4 of the issue.

 Knowledge of how the following Windows

components integrate with Citrix technologies:

o Active Directory Domain Services

o Active Directory Certificate Services

o Policies

o Domain Name System (DNS)

o Dynamic Host Configuration Protocol (DHCP)

o Group Policy Objects (GPOs)

o NTFS Permissions

o Authentication and Authorization

o Knowledge of IIS

o Microsoft Windows Operating Systems

 Windows 10

 Windows 8.1

 Windows 7

 Windows Server 2012 R2

 Windows Server 2008 R2

 Roles and features of Windows Server

 Knowledge of SQL 2008 R2 and newer

 Knowledge of SQL Clustering, Mirroring and

AlwaysOn Availability Groups.

 General networking skills (i.e. routing, switching)

 Knowledge of hypervisors.

 Knowledge of shared storage configuration and

management.

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Level-4

(Architect)

The Level-4 team has

minimal exposure to

administrative tasks but

focuses on scoping,

planning and executing

Citrix-specific service and

project requests. An

architect translates

business requirements

into a technical design.

 Provide technical leadership for upcoming

projects.

 Lead design updates and architecture revisions.

 Address high severity issues and service outages

 Oversee technology integration workflows.

 Review periodic reports of server health, resource

usage, user experience, and overall environment

performance to determine next steps and upgrade

paths.

 Initiate load testing to determine capacity of

environment.

 Review frequently recurring helpdesk issues

 Ensure technical specifications continue to meet

business needs.

 Update design documentation.

 Advanced architectural assessment and design

skills for:

o Citrix XenApp

o Citrix XenDesktop

o Citrix XenServer / VMware vSphere / Microsoft

Hyper-V

o Citrix Provisioning Services

o Citrix NetScaler

o Citrix StoreFront

o Active Directory

o Storage solutions

o Networking

o Application delivery

o Disaster recovery

o Policies/policy structures and security

restrictions

o Licensing

o Methodology

 Intermediate knowledge of:

o General networking skills

o Change control process

o Project management

o Risk assessment

Vendor

Support

Vendor assistance may be necessary should defects in a program be discovered. At this stage, Level-3 engineers need to establish a support

ticket with the appropriate vendor to assist with finding a solution.

Self-Service

A self-service portal should be utilized for noncritical tasks such as application access, permissions, password resets, etc. The portal can range

from a simple FAQ page to a fully automated process requiring no human interaction. The purpose of the self-service portal is to add an

additional touch point for end users to address basic issues, preventing the creation of new support tickets.

Table 62: Support Levels

Decision: Certifications and Training

The following table details the recommended training, certifications and experience for each support level.

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Role

Recommended Training

Recommended

Course(s)

Recommended

Certification

Relevant

Experience

Help Desk

(Level 1)

Level-1 support personnel should be provided with basic training on Citrix

XenApp, Citrix XenDesktop and supporting technologies. This can include

internal training from subject matter experts or from a Citrix Authorized

Learning Center. The training provided should focus on the following

topics:

 High level overview of the XenApp and XenDesktop implementation

 Using Citrix Director to manage user sessions

 Troubleshooting Citrix XenApp and XenDesktop sessions

 Troubleshooting methodology

In addition, regular training should be provided to the Tier-1 team

members on the latest troubleshooting recommendations from the Level-

2 and Level-3 teams as well as details on any relevant changes to the

environment. This will help to ensure a good baseline knowledge level

across the team and consistent customer service.

CXD-105: Citrix

XenApp and

XenDesktop Help

Desk Support

N/A

1+ years

(Entry level also

acceptable)

Operator

(Level-2)

Level-2 personnel should conduct regular team training sessions to refine

administrative skills and ensure a baseline knowledge level across the

team.

Formalized trainings are also essential when there are architectural

updates to the environment and the Level-2 team is working with

unfamiliar technologies. All members of the Level-2 team should achieve

the Citrix Certified Associate (CCA) certification for Citrix XenApp and

XenDesktop. Advanced training on Windows concepts will also be

essential for Level-2 team members who do not have desktop or server

support experience.

Finally, on-the-job training along with close integration with Level-3

administrators is essential as the Level-2 roles are formalized and

responsibilities are handed over from Level-3 to Level-2.

CXD-210: XenApp

and XenDesktop

7.1x Administration

Citrix Certified

Associate -

Virtualization

2-3 years

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Implementer

(Level-3)

Level-3 support team members hold a minimum of three years of

enterprise experience implementing and supporting XenApp, XenDesktop,

Provisioning Services and Windows operating systems.

Level-3 staff should also complete the Citrix Certified Professional (CCP)

certification track as this will prepare them to proactively manage the user

community and implement Citrix solutions according to Citrix leading

practices.

CXD-310: XenApp

and XenDesktop

7.1x Advanced

Administration

after completion of

level-2 CXD-210

Citrix Certified

Professional -

Virtualization

3-4 years

Architect

(Level 4)

Experience is essential for Level-4 staff. A qualified Level-4 resource should

have a minimum of five of experience implementing, supporting, and

serving in a technology architect role for a XenApp and/or XenDesktop

environment as well as additional administrative experience with

integrated technologies such as application and profile management

solutions. The ideal candidate will have served in such a capacity at two or

more environments for purposes of product exposure and in at least one

environment of over 1,200 concurrent users. A Citrix Certified Expert (CCE)

certification or comparable training and experience should be a

prerequisite of the role.

CXD-400:

Designing App and

Desktop Solutions

with Citrix XenApp

and XenDesktop

after completion of

level-3 CXD-310

Citrix Certified

Expert -

Virtualization

5+ years

Table 63: Training Recommendations

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Decision: Support Staffing

The following table provides guidance on the recommended number of support staff.

Role

Small Environment

Sites: 1

Users: <500

Images: 1-2

Mid-size Environment

Sites: 1-2

Users: 1000-5000

Images: 3-5

Large Environnent

Sites: 2+

Users: >5000

Images: 5+

Help Desk (Level-1)

5-10

15-20

Operator (Level-2)

1-2

2-3

4-5

Implementer (Level-3)

1-2

2-3

Architect (Level-4)

1-2

Note: This table should only be used as a baseline. Support staffing decisions should be evaluated

against the defined requirements, projected workloads, and operational procedures of an

organization. Multiple levels can be combined, for example there may be insufficient design projects

to have a dedicated architect role or a more senior member of the Citrix team can act as an Operator

and Implementer.

Decision: Job Aids

General Support Tools

The following table details tools that should be made available to all support levels.

Tools

Details

Ticket Management System

Used to document customer information and issues. A typical ticket

management system provides the following functionality:

 Monitoring the queue of tickets.

 Setting a limit on the number of open tickets.

 Establishing thresholds such as how long a certain type of ticket

should take to be answered.

 Identifying a group of users or individuals who require higher

priority assistance.

 Informing the user when their ticket is open, updated, or closed.

 Provide an internal knowledge base for the support professionals

to search for known resolved issues.

Call Scripts

The first contact help desk personnel should have documented scripts to

ensure that all relevant data is captured while the user is on the phone. This

practice also assists in proper triage and allows the next support level to

perform research prior to customer contact. A sample call script is provided

for reference.

Remote Assistance Tools

Remote assistance tools are useful when troubleshooting user issues.

Support technicians and administrators can remotely observe a user’s

actions.

Knowledge Base

Documentation should be created and maintained in a knowledge base or

library of known issues. Articles should be searchable for quick recovery.

Knowledge bases help support staff to quickly resolve known issues and

reduce the need to perform time consuming research.

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Table 64: Recommended General Helpdesk Tools

Citrix Support Tools

The following table provides recommendations on the Citrix support tools that should be made

available to each support level.

Tool

Description

Products

Support Level

PVS

Citrix Director

Citrix Director provides an overview of

hosted desktops and application

sessions. It enables support teams to

perform basic maintenance tasks and to

monitor and troubleshoot system issues.

Citrix Studio

Citrix Studio enables administrators to

perform configuration as well as

maintenance tasks for a

XenApp/XenDesktop site and associated

virtual desktops or hosted applications.

Citrix Insight

Services

Run from a single Citrix Delivery

Controller to capture key data points and

CDF traces for selected computers

followed by a secure and reliable upload

of the data package to Citrix Technical

Support for escalation.

HDX Monitor

HDX Monitor is a tool to validate the

operation of the Citrix ICA/HDX stack of a

user session. HDX Monitor provides

information about client capabilities,

network performance / activity, session

settings and many more items.

Provisioning

Services

Console

The Provisioning Services Console

enables administrators to perform

configuration and maintenance tasks for

a Provisioning Services farm.

XenCenter

XenCenter enables administrators to

perform configuration and maintenance

tasks for a XenServer Resource Pool.

Table 65: Support Citrix Tool Assignment

Citrix Insight Services

Administrators can utilize Citrix Insight Services to simplify the support and troubleshooting of

the Citrix environment. Citrix Insight Services is run locally to collect environment information.

Online analysis capabilities analyze that information and provide administrators

recommendations based on their Citrix environment and configuration. Additional information

regarding Citrix Insight Services can be referenced in the Citrix Support article CTX131233 - FAQ:

Citrix Insight Services.

A full list of the available tools provided by Citrix Support to assist with troubleshooting can be

referenced in Citrix Supportability Pack.

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Call Script

The following call script can be used as an initial baseline for a Citrix Help Desk team. Citrix

Consulting recommends reviewing this sample call guide and adding any environment specific

details that may need to be collected.

Step

Details

What is the name and location of the user?

This question will identify if the user is accessing the environment from an external or internal

network location.

Is the problem always reproducible? If it is a Yes, get the exact reproduce steps.

This question is very important for the support team to troubleshooting an issue.

Do any other users at the site/location experience the same issue? Can they have a colleague

logon from same and/or different workstation?

These questions help to determine if this is a workstation issue or a user issue.

What type of endpoint device is the user utilizing? (Corporate device, BYOD, thin client, pc, laptop,

etc.)

This question will help determine if the issue is related to the user’s endpoint.

What is the Citrix Receiver version and connection information?

This question will verify if the user is using the right version of Receiver (the latest Receiver version

or the version standardized by the company).

Can the user see the StoreFront authentication page?

This question helps to identify network issues.

What is the name of the application (or virtual desktop) the user is attempting to use? Does the

user see the appropriate application or desktop icon on the StoreFront site?

These questions help to determine if there is an issue with user access and/or group membership.

Does the application (or desktop) launch when the icon is selected? Does the application logon

screen appear (if applicable)?

These questions help to determine if a connection is made into the Citrix XenDesktop

infrastructure.

Can the user authenticate into the application (if applicable)? Does the issue occur after the

application is launched?

This question helps to determine if the issue is with the application rather than the application

delivery infrastructure.

10.

What is the specific error seen (if applicable)? Get screen captures

This question identifies the specific error. The user should be requested to provide a screenshot, if

available.

Decision: Delegated Administration

Each support level must be provided with sufficient rights to effectively perform their role. The

following tables provide guidance on the recommended privileges per support level.

XenApp/XenDesktop Delegated Rights

Admin Role

Support Level

Help Desk Administrator

Level-1

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Full Administrator

Level-2

Full Administrator

Level-3

Full Administrator

Level-4

Table 66: XenApp/XenDesktop Delegated Rights

For further information about delegated rights within a XenApp/XenDesktop Site, please refer to

Citrix Product Documentation - XenApp and XenDesktop Delegated Administration.

Provisioning Services Delegated Rights

Admin Role

Support Level

N/A

Level-1

Site Administrator

Level-2

Farm Administrator

Level-3

Full Administrator

Level-4

Table 67: Provisioning Services Delegated Rights

For further information about delegated rights within a Provisioning Services Site, please refer to

Citrix eDocs - Provisioning Services Managing Administrative Roles.

StoreFront Delegated Rights

Admin Role

Support Level

N/A

Level-1

N/A

Level-2

Local Administrator on SF server

Level-3

Full Administrator

Level-4

Table 68: StoreFront Delegated Rights

Users with local administrator rights have access to view and manage all objects within

StoreFront or Web Interface. These users can create new sites and modify existing ones.

Citrix License Server Delegated Rights

Admin Role

Support Level

N/A

Level-1

N/A

Level-2

Administrator

Level-3

Administrator

Level-4

Table 69: Citrix License Server Delegated Rights

By default, the account used during the installation of the license server becomes the

administrator for the console. Often the accounts used for the installation are not the intended

accounts for the regular administration tasks. For the steps on how to change the default

administrator, please reference CTX135841 - How to Change the Default Administrator for the

Citrix Licensing Server Version 11.10. All users created through this process are full administrators

of the Citrix License Server.

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XenServer Delegated Rights

Admin Role

Support Level

N/A

Level-1

Virtual Machine Operator

Level-2

Pool Administrator

Level-3

Full Administrator

Level-4

Table 70: XenServer Delegated Rights

For further information about delegated rights within a XenServer Resource Pool, please refer to

XenServer 7.0 Administrators Guide (see chapter Role Based Access Control).

Process 2: Operations

This section defines routine operations for the Citrix environment that help to improve stability and

performance.

Decision: Administrative Tasks

The Citrix Support Team should perform regular operations and maintenance tasks to ensure a

stable, scalable Citrix environment.

Each operation is categorized by the associated component of the solution as well as the frequency

of the operation (ongoing, daily, weekly and yearly). Tasks have been aligned to the roles described

within Decision: Support Responsibilities and Skill Set.

If the administrators performing operations are the same the support team, then the designations

are linked as follows:

 Level 2 Support = Operators

 Level 3 Support = Implementers

Daily Periodic Tasks

The following table outlines the tasks that should be performed by the Citrix Support Team on a

daily basis.

Component

Task

Description

Responsible

Generic

Review Citrix

Director,

Windows

Performance

Monitor, Event

Log, and other

monitoring

software alerts

Check for warnings or alerts within Citrix Director, event

logs, or other monitoring software. Investigate the root

cause of the alert if any.

Note: A computer and monitor can be set up to display

the Citrix Director dashboard to create a Heads Up

Display for the Citrix department. This ensures the

status of the environment is clearly visible.

Monitoring recommendations for XenDesktop and

XenApp 7.x are included in the Monitoring section of

the VDI Handbook.

Operators

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Generic

Verify backups

completed

successfully

Verify all scheduled backups have been completed

successfully. This can include but is not limited to:

 User data (user profiles / home folders)

 Application data

 Citrix databases

 StoreFront configuration

 Web Interface configuration

 Provisioning Services vDisks (virtual desktops

and application servers)

 XenServer VM/Pool metadata (or equivalent

for other hypervisors)

 Dedicated virtual desktops

 License files

Operators

Generic

Test

environment

access

Simulate a connection both internally and externally to

ensure desktop and application resources are available

before most users log on for the day. This should be

tested throughout the day and may even be

automated.

Operators

XenApp/

XenDesktop

Virtual machine

power checking

Verify that the appropriate number of idle desktops

and application servers are powered on and registered

with the Delivery Controllers to ensure availability for

user workloads.

Operators

XenApp/

XenDesktop

Perform

incremental

backup of Citrix

databases

Perform incremental-data backups of the following

Citrix databases:

 Site Database

 Configuration Logging Database

 Monitoring Database

Operators,

Database team

(if Citrix

environment is

using a shared

SQL)

Provisioning

Services

Check Citrix

Provisioning

Server utilization

Check the number of target devices connected to the

Citrix Provisioning Servers and balance the load across

servers, if required.

Operators

Provisioning

Services

Perform

incremental

backup of Citrix

PVS database

Incremental backup of Citrix Provisioning Server

database hosted on SQL Server infrastructure.

Operators,

Database team

(if Citrix

environment is

using a shared

SQL)

Table 71: Daily Operations

Weekly Periodic Tasks

The following table outlines the tasks that should be performed by the Citrix Support Team on a

weekly basis.

Component

Task

Description

Responsible

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Generic

Review latest

hotfixes and

patches

Review, test, and deploy the latest Citrix hotfixes and

ascertain whether the Delivery Controllers and Server-

Based OS / Desktop-Based OS virtual machines require

them.

Note: Any required hotfixes should be tested using the

recommended testing process prior to implementation

in production.

Operators,

Implementers

(review

process)

Generic

Create Citrix

environment

status report

Create report on overall environment performance

(server health, resource usage, user experience) and

number of Citrix issues (close rate, open issues, and so

on).

Operators

Generic

Review status

report

Review Citrix status report to identify any trends or

common issues.

Implementers,

Architect

Generic

Maintain internal

support

knowledge base

Create knowledge base articles and issue resolution

scripts to address Level-1 and Level-2 support requests.

Review knowledge base articles and issue resolution

scripts for accuracy, compliance, and feasibility.

Operators

(Level-2

requests),

Implementers

(Level-3

requests, and

review process)

XenApp/

XenDesktop

Check

Configuration

Logging reports

Confirm that Citrix site-wide changes implemented

during the previous week were approved through

change control.

Auditors

XenApp/

XenDesktop

Perform full

backup of Citrix

databases

Perform full-data backups of the following Citrix

databases:

 Site Database

 Configuration Logging Database

 Monitoring Database

Operators,

Database team

(if Citrix

environment is

using a shared

SQL)

Provisioning

Services

Check storage

capacity

(only prior to

updating a vDisk)

Review storage utilization, used and free storage space,

for vDisk store and each vDisk.

Note: Lack of space within the vDisk repository will be

an issue only when the vDisks are updated using

versioning or when a vDisk is placed in private mode

during an update procedure.

Storage utilization within vDisk should also be

investigated. For example, a 20GB vDisk may only have

200MB of free storage. If the vDisk itself is limited for

storage, then it needs to be extended. Citrix does not

support resizing of a VHD file. Refer to the Microsoft

link Resize-VHD for information on resizing a VHD file.

Operators

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Provisioning

Services

Perform vDisk

updates (as

necessary)

Perform a full backup of the vDisk before

implementing any updates.

Update the master vDisk image files and apply the

following:

 Windows software updates and patches

 Operating system and application changes

 Anti-virus pattern and definitions updates

Note: Updates should be tested using the

recommended testing process prior to implementation

in production.

Operators

Provisioning

Services

Check auditing

reports

Review the Citrix Provisioning Services auditing Logs.

Note: Provisioning Server auditing is off by default and

can be enabled to record configuration actions on

components within the Provisioning Services farm. To

enable auditing refer to the Citrix eDocs article

Enabling Auditing Information

Auditors

Provisioning

Services

Perform full

backup of Citrix

PVS database

Backup of Citrix Provisioning Server database hosted

on SQL Server infrastructure.

Operators,

Database team

(if Citrix

environment is

using a shared

SQL)

Table 72: Weekly Operations

Monthly Periodic Tasks

The following table outlines the tasks that should be performed by the Citrix Support Team on a

monthly basis.

Component

Task

Description

Responsible

Generic

Perform capacity

assessment

Perform capacity assessment of the Citrix environment

to determine environment utilization and any scalability

requirements.

Note: Recommendations for performing a capacity

assessment are included in Decision: Capacity

Management in the Monitoring section of the Virtual

Desktop Handbook.

Architect

Table 73: Monthly Operations

Yearly Periodic Tasks

The following table outlines the tasks that should be performed by the Citrix Support Team on a

yearly basis.

Component

Task

Description

Responsible

Generic

Conduct Citrix

policy

assessment

Review Citrix policies and determine whether new

policies are required and existing policies need to be

updated.

Implementers

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Generic

Review software

upgrades

Review and assess the requirement for new Citrix

software releases or versions.

Architect

Generic

Perform

Business

Continuity Plan

(BCP)/ Disaster

Recovery (DR)

test

Conduct functional BCP/DR test to confirm DR

readiness.

This plan should include a yearly restore test to validate

the actual restore process from backup data is

functioning correctly.

Implementers

Generic

Perform

application

assessment

Review the usage of applications outside and within

the Citrix environment. Assess the validity of adding

additional applications to the Citrix site, removing

applications that are no longer required, or upgrading

the applications to the latest version.

Architect

Provisioning

Services

Archive audit

reports

Perform an archive of the Citrix Provisioning Server

Audit Trail Information for compliance requirements.

Auditors

Decision: Backup Location

The location of backups directly effects the recovery time and reliability of the Citrix environment. It

is recommended to store backups of critical data both onsite and at an offsite location. If offsite

backups are not possible due to costs associated or sensitivity of the data, backups should be placed

at separate physical locations within the same datacenter.

Each backup option is discussed further below.

 Onsite Backups – Onsite backups should be located on a storage device in the datacenter

that will allow the data to be recovered quickly in the event of a failure. Onsite backups are

ideal for issues that only affect a small subnet of hardware in the datacenter. Backups can

also be stored on a cold storage solution such as tape. While this medium is slower to

recover from, it provides additional protection since it is only active during the backup

process.

 Offsite Backups – Although the time to recover is much higher, offsite backups provide

additional protection in the event of a disaster. Offsite backups may require transferring

data over the Internet to a third party provider or they are created onsite and then

transported to a remote location on storage mediums such as tape. It is typical to put a

limited number of backups offsite. For example, one backup a week or month.

Decision: Testing Process

Regular updates and maintenance are an everyday part of IT operations. Standard processes must

be followed to ensure updates do not negatively impact the production environment. This includes

maintaining a dedicated testing infrastructure where modifications can be validated prior to being

implemented in production.

Since changes to Citrix infrastructure can impact thousands of virtual desktop and application users,

multi-phase testing is critical for the reliability and performance of the environment. As such, the

process for testing should resemble the following:

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Figure 42: Testing Process

 Development - The development infrastructure exists outside of the production network.

Typically, it consists of short-lived virtual machines whose configuration matches

production as closely as possible. The purpose of the development phase is to provide

change requestors a non-production environment to perform proof of concepts, determine

integration requirements and perform iterative testing as part of a discovery phase.

Proposed changes should be documented so they can be applied in the test phase.

 Testing - The test environment is a standalone 1:1 copy of the production infrastructure and

is used to confirm that the proposed changes can be easily repeated prior to the pre-

production staging environment. The changes made should follow documentation from

the development stage. If testing fails within the testing stage, the architect must determine

the severity of failure and determine whether minor updates to documentation is sufficient

or a full development cycle is needed.

 Pre-production - The pre-production environment should mimic the current production

environment. The goal of staging is to implement the proposed changes with little risk or

uncertainty. It is expected that any changes made to the staging infrastructure have been

tested and documented for repeatability. There should not be any iterations or adjustments

required within this phase. During this phase and within this environment User Acceptance

Testing (UAT) should be performed.

 Production - The production environment is a fully redundant and scalable solution

designed for normal usage by end users. There should be minimal changes to the

environment. If possible, all approved changes should be rolled out in stages to the

production environment. This process is known as a staged rollout and mitigates risk by

allowing changes to be rolled back, if necessary, without impacting the entire environment.

Decision: Change Control

Standardized processes that manage changes throughout a system’s lifecycle are necessary to

ensure consistent and accountable performance. The following change control leading practices

should be considered.

 Use a change control window so that all applicable parties know when there might be

downtime.

 Make sure that all teams are represented in the Change Advisory Board (CAB).

 Every change should have a roll back plan.

 If a change fails have a “hot wash” to determine what went wrong.

 Always use an automated change control system so that support staff can quickly and easily

identify changes.

 When available, ensure configuration logging is enabled to track any changes made to the

Citrix environment.

Change

Request

Development Testing

Pre-

production

Production

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The change control process should be closely followed starting with a change request. A change

request form should be filled out detailing changes requested, reasons for the change, and

intended timeframes for the action. This is then reviewed and edited if required by a Change

Manager and advisory board. When the change request has gone through the entire change

approval process it is given to a change implementer who stages the change for testing, and finally

conducts the implementation in production.

A sample change control process, including detailed steps, is provided in the diagram below:

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Figure 43: Change Control Process

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The process is as follows:

1. The Change Request (CR) form is completed by any person requesting a change.

2. After appropriate manager approvals have been acquired, the CR is forwarded to the

appropriate Change Manager(s).

3. The Change Manager validates the CR for completeness and logs the CR information into

the Change Control Log for tracking. Incomplete change requests are returned to the

requestor for update and re-submission.

4. The Change Manager assesses the impact of the change in conjunction with subject matter

experts and/or managers of the teams associated/affected by this change.

5. The Change Manager works with the associated/affected teams as well as the change

requestor in order to confirm the priority, category and type of the change as well as the

proposed rollback plan.

6. If the change is approved by the Change Manager, the CR is forwarded to the CAB for

approval. If the change is rejected, the Change Control Log is updated with the current

status as well as the reason of the rejection and the CR is send back to the requestor.

7. The CAB reviews and validates the change in detail, and discusses and evaluates purpose,

reasons, impact, cost and benefits. Each board member represents their department and

provides guidance on the change requests. The CAB also reviews multiple requests to

coordinate implementations and “package” requests into a single release schedule.

8. Upon approval the change is sent back to the Change Manager to schedule the change for

implementation into the staging environment.

9. The change is implemented and tests are conducted. The results are sent back to the

Change Manager.

10. If the staging implementation and testing are successful, the change is scheduled for

production implementation. In case the staging phase was not successful another staging

iteration will be conducted.

11. If possible, the change is rolled out in stages to the production environment. This process is

known as a staged rollout and mitigates risk by allowing changes to be rolled back, if

necessary, without impacting the entire environment. A rollback plan should be in place if

there is an issue implementing a change in the production environment.

12. The Change Manager reviews the implementation and finally updates the Change Control

Log.

13. On a periodic basis, the Change Manager reviews the Change Control Log to identify trends

on type, frequency and size of changes and forwards the results to the CAB for review.

In an emergency, the processes may be expedited. Should an issue be declared an emergency, a

change request form is still filled out and delivered to the appropriate change management

representative. When approved, the requested change is immediately implemented and the

advisory board notified.

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Decision: Availability Testing

Availability testing is focused on ensuring resources are still available in the instance of a component failure. These tests are essential to ensuring

users always have access to business critical resources. The testing should be conducted during nonbusiness hours or during a scheduled

maintenance weekend when appropriate notice has been given to end users to make them aware if any unforeseen issues arise.

The following is a list of the key components that should be tested on a regular basis.

 StoreFront – StoreFront should be load balanced and health checked by a NetScaler or other load balancing device. To validate its

configuration, all but one of the StoreFront servers should be shutdown. This will validate that the load balancing device is detecting the

failure and directing users to the functioning server.

 SQL – SQL Server should be in a high availability configuration. To validate the configuration, the primary SQL server should be taken

offline and then the Citrix Studio console should be opened. Since Citrix Studio will not be accessible without a functioning SQL server, it

will validate that the SQL server failover mechanisms are functioning properly.

 Delivery Controllers - Resources deployed should be configured with a list of multiple Delivery Controllers. If one is made unavailable,

desktops and application hosts will automatically establish a connection to another server in the list. To validate this, shutdown one of

the Delivery Controller hosts and determine if the resources initially connected to it automatically register to another server. This can be

determined by viewing the registration status of the resources inside Citrix Studio.

Sample Testing Workflow: Citrix Provisioning Services

Prerequisites and configuration requirements:

 Hypervisor, XenApp, and XenDesktop services are up and running.

 At least two PVS servers are installed and configured, providing the streamed disk image.

 Resilient networking and storage infrastructure with multiple links to each server.

 Test users are active on the XenApp or XenDesktop machines.

Steps

Expected Results

PVS Server Outage

 Shutdown one of the Provisioning Servers.

 Validate PVS continues to function.

 Restart PVS Server.

 Validate connections rebalance between PVS Servers.

 Try the other(rest) PVS server(s) one by one.

 Existing XenApp/XenDesktop machines connect to another PVS server.

 There is limited to no impact to the users utilizing that server.

 New XenApp/XenDesktop machines can be booted and start correctly.

 SCOM reports that the PVS server is down / not available.

 Live connections are rebalanced between both PVS servers once both PVS

servers are made available again.

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PVS Bond Disruption

 Disable / unplug a NIC in the PVS Streaming Bond on

the PVS server.

 Provisioning Server continues to stream over remaining NICS in PVS

Streaming Bond.

SQL Server PVS Database Mirror Failover

 Admin logs on to Principle SQL Server.

 Initiate failover of PVS database.

 Validate PVS continues to function.

 Initiate failback of PVS database.

 Validate PVS continues to function.

 PVS continues to function.

SQL Service Outage

 Admin reboots both Principle & Mirror SQL Servers

simultaneously.

 Validate PVS continues to function, but that

administration is not possible.

 Wait for the SQL Server to come back online.

 Validate PVS administrative functions are once again

possible.

 PVS continues to function.

 PVS administrative functions are no longer available.

 PVS administrative functions are available once the SQL services are

restored.

Sample Testing Workflow: Citrix XenDesktop and XenApp Services

Prerequisites and configuration requirements:

 Hypervisor, XenDesktop, and StoreFront services are up and running.

 Network and storage services available.

 Provisioning Services is providing the streamed disk images.

 Test users are active on the virtual machines.

 SQL (Mirroring) and XenDesktop servers are up and running.

 Ensure multiple StoreFront servers are running.

 NetScaler load balancing services.

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Steps

Expected Results

XenApp/XenDesktop 7.x Delivery Controller Citrix Broker Service

Outage:

 Stop the Citrix Broker Service on one of the Delivery

Controller servers.

 Validate virtual desktops or applications can still be

enumerated and launched.

 Start the Citrix Broker Service on the Delivery Controller

server.

 Shutdown one of the Desktop Controllers.

 Validate virtual desktops or applications can still be

enumerated and launched.

 With a desktop launched, determine which Controller

owns the host connection. Shut the Controller down

and verify that another Controller takes over the session.

Note: This should be done during the maintenance window. Once

complete, the VDI resources should be rebooted so the VDAs are

evenly distributed across all controllers.

 StoreFront correctly identifies service as being unavailable and redirects

connections to remaining Delivery Controller.

 Desktops continue to be enumerated and launch successfully.

 Launched desktop can be supported if a hosting Controller goes down.

SQL Server Database Mirror Failover:

 Admin logs on to principle SQL Server.

 Initiate failover of XenApp/XenDesktop database.

 Validate XenApp/XenDesktop continues to function.

 The database should failover and the Citrix Studio should pick up the

failover database with no issues.

 Existing sessions are not impacted.

 New sessions are possible.

 Administrative functions are possible.

SQL Service Outage:

 Admin restarts both principle & mirror SQL Servers

simultaneously.

 Validate XenApp/XenDesktop continues to function, but

that administration is not possible.

 Wait for the SQL Service to come back online.

 Validate administrative functions are once again

possible.

 Existing XenDesktop sessions are not impacted

 Recently used applications, hosted shared desktops and assigned VDI can

be accessed due to local host cache.

 XenDesktop Administrative functions are not possible

 XenDesktop Administrative functions are possible once SQL service is

available.

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Sample Testing Workflow: Citrix Licensing Services

Prerequisites and configuration requirements:

 Citrix Licensing Server up and running (with valid licenses installed).

 Hypervisor, XenApp/XenDesktop and StoreFront services are up and running.

 Users are active on the Server OS or Desktop OS machines.

Steps

Expected Results

Service continuity during complete failure of the Citrix Licensing

Server:

 Shutdown the Citrix Licensing server.

 Reboot an existing Server OS machine.

 Logon to the Citrix StoreFront and launch a published

application.

 Reboot an existing Desktop OS machine.

 Logon to the Citrix StoreFront and launch a virtual

desktop.

 License Server connectivity error posted in Event Log.

 Provisioned Server OS boots successfully.

 Users are able to launch published applications.

 Provisioned Desktop OS boots successfully.

 User is able to launch a virtual desktop.

 Administrators will have 30 days grace to recover the Citrix Licensing Server.

Process 3: Monitoring

By having an in-depth understanding of current and expected behavior of the Citrix environment and its components, administrators are better

equipped to discover an issue before it affects the user community. Furthermore, the data tracked during normal operations is beneficial for

trending and capacity planning. This section defines the monitoring recommendations for a Citrix environment as well as some recommended tools.

Decision: Automated Monitoring

Depending on the size and scope of the XenApp and XenDesktop solution, it can take considerable time for an administrator to verify services,

events, capacity and performance. It is advisable for administrators to investigate automation into their monitoring strategy.

Citrix includes a cloud-hosted monitoring solution called Smart Check (https://smart.cloud.com), which is a free service for any organization with

active Citrix Customer Success Services: Select offering. Smart Check executes the following in a XenApp and XenDesktop environment:

 Site Health Checks – Evaluates all services with the XenApp and XenDesktop site

 Apps and Desktops Checks = Verifies delivery group availability

 Update Checks – Tracks and recommends patches and hotfixes for delivery controllers

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 LTSR Checks – Verifies the delivery controllers and VDAs within the site comply with LTSR versions.

 Custom Checks – Allows administrators to import their own custom scripts to test across their XenApp and XenDesktop site.

A list of the current Smart Check capabilities, review the Smart Check documentation.

Decision: Performance Monitor Metrics

Monitoring the performance of the overall environment is crucial towards making sure all components are available and performing effectively to

ensure users have a high quality experience.

Different components within the overall solution require monitoring of unique metrics with appropriately set thresholds. The metrics and

thresholds presented are based on real world experience but may not apply to all environments. Organizations will need to perform their own

baselining, validity testing and validation before implementing within a production environment.

Note: Some hypervisors, such as VMware vSphere and Hyper-V, provide specific performance counters for tracking CPU and Memory utilization

within virtual machines (i.e. “VM Processor \ % Processor Time”). These performance counters should be used in addition to the general counters

listed below.

General

These performance counters should be used to monitor the key performance metrics of the Citrix infrastructure, application servers, and

virtual desktops.

Metric

Description

Warning

(Yellow)

Critical

(Red)

Troubleshooting / Remediation

Processor - %

Processor Time

% Processor Time is the percentage of elapsed time

that the processor spends to execute a non-Idle

thread. It is calculated by measuring the duration of

the idle thread is active in the sample interval, and

subtracting that time from interval duration. (Each

processor has an idle thread that consumes cycles

when no other threads are ready to run). This counter

is the primary indicator of processor activity, and

displays the average percentage of busy time

observed during the sample interval. It is calculated

by monitoring the time that the service is inactive and

subtracting that value from 100%.

80% for 15

minutes

95% for 15

minutes

Identify the processes/services consuming

processor time using Task Manager or Resource

Monitor.

If all processes/services work within normal

parameters and the level of CPU consumption is

an expected behavior it should be considered to

add additional CPU resources to this system in

the future.

If a process/service can be identified which

works outside normal parameters, the process

should be killed. Please note that killing a

process can cause unsaved data to be lost.

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System - Processor

Queue Length

Processor queue length is the number of threads in

the processor queue. Unlike the disk counters, this

counter shows ready threads only, not threads that

are running. There is a single queue for processor

time even on computers with multiple processors.

Therefore, if a computer has multiple processors, you

need to divide this value by the number of processors

servicing the workload. A sustained processor queue

of less than ten threads per processor is normally

acceptable, dependent of the workload.

5 (per core)

for 5

minutes

6 (per core)

for 15

minutes

10 (per

Core) for 10

minutes

12 (per

core) for 30

minutes

A long CPU queue is a clear symptom of a CPU

bottleneck. Please follow the steps outlined for

counter “Processor - % Processor Time”.

Memory – Available

Bytes

Available memory indicates the amount of memory

that is left after nonpaged pool allocations, paged

pool allocations, process’ working sets, and the file

system cache have all taken their piece.

<30% of

total RAM

20% of

physical

memory

over 6

minutes

<15% of

total RAM

5% of

physical

memory

over 6

minutes

Identify the processes/services consuming

memory using Task Manager or Resource

Monitor.

If all processes/services work within normal

parameters and the level of memory

consumption is an expected behavior it should

be considered to add additional memory to this

system in the future.

If a process/service can be identified which

works outside normal parameters, the process

should be killed. Please note that killing a

process can cause unsaved data to be lost.

Memory – Pages/sec

Pages/sec is the rate at which pages are read from or

written to disk to resolve hard page faults.

>10

>20

A high value reported for this counter typically

indicates a memory bottleneck, except if

“Memory – Available Bytes” reports a high value

at the same time. In this case most likely an

application is sequentially reading a file from

memory. Please refer to Microsoft Knowledge

Base article KB139609 – High Number of

Pages/Sec Not Necessarily Low Memory for

further information.

Paging File - %Usage

This is the percentage amount of the Page File

instance in use.

>40%

80% over 60

minutes

>70%

95% over 60

minutes

Review this value in conjunction with “Memory -

Available Bytes” and “Memory - Pages/sec” to

understand paging activity on the affected

system.

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LogicalDisk/PhysicalDi

sk - % Free Space

% Free Space is the percentage of total usable space

on the selected logical disk drive that is free.

<20% of

physical disk

20%

reported

after 2

minutes

<10% of

physical disk

15%

reported

after 1

minute

Identify which files or folders consume disk

space and delete obsolete files if possible. In

case no files can be deleted, consider increasing

the size of the affected partition or add

additional disks.

LogicalDisk/PhysicalDi

sk - % Disk Time

% Disk Time marks how busy the disk is.

>70%

consistently

90% over 15

minutes

(_Total)

>90%

consistently

95% over 15

minutes

(_Total)

Identify the processes / services consuming disk

time using Task Manager or Resource Monitor.

If all processes/services work within normal

parameters and the level of disk consumption is

an expected behavior it should be considered to

move the affected partition to a more capable

disk subsystem in the future.

If a process/service can be identified which

works outside normal parameters, the process

should be killed. Please note that killing a

process can cause unsaved data to be lost.

LogicalDisk/PhysicalDi

sk – Current Disk

Queue Length

Current disk queue length provides a primary

measure of disk congestion. It is an indication of the

number of transactions that are waiting to be

processed.

>=1 (per

spindle)

consistently

3 over 15

minutes

(_Total)

>=2 (per

spindle)

consistently

10 over 30

minutes

(_Total)

A long disk queue length typically indicated a

disk performance bottleneck. This can be

caused by either processes/services causing a

high number of I/Os or a shortage of physical

memory. Please follow the steps outlined for

counter “LogicalDisk/PhysicalDisk - % Disk Time”

and counter “Memory – Available Bytes”

LogicalDisk/PhysicalDi

sk – Avg. Disk

Sec/Read

– Avg. Disk Sec/Write

– Avg. Disk

Sec/Transfer

The Average Disk Second counters show the average

time in seconds of a read/write/transfer from or to a

disk.

>=15ms

consistently

>=20ms

consistently

High disk read or write latency indicates a disk

performance bottleneck. Systems affected will

become slow, unresponsive and application or

services may fail. Please follow the steps

outlined for counter “LogicalDisk/PhysicalDisk -

% Disk Time”

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Network Interface –

Bytes Total/sec

Bytes Total/sec shows the rate at which the network

adaptor is processing data bytes. This counter

includes all application and file data, in addition to

protocol information, such as packet headers.

< 8 MB/s for

100 Mbit/s

adaptor

<80 MB/s

for 1000

Mbit/s

adaptor

60% of NIC

speed

inbound

and

outbound

traffic for 1

min.

70% of NIC

speed

inbound

and

outbound

traffic for 1

min.

Identify the processes / services consuming

network using Task Manager or Resource

Monitor.

If all processes/services work within normal

parameters and the level of bandwidth

consumption is an expected behavior it should

be considered to move the respective

process/service to a dedicated NIC (or team of

NICs).

If a process/service can be identified which

works outside normal parameters, the process

should be killed. Please note that killing a

process can cause unsaved data to be lost.

Table 74: Recommended Metrics to Monitor for all Virtual Machines

XenApp/XenDesktop

These performance counters are specific to the Delivery Controllers.

Metric

Description

Warning

(Yellow)

Critical

(Red)

Troubleshooting / Remediation

Database Avg.

Transaction Time

The time on average, in seconds, taken to execute a

database transaction. A baseline needs to be

established in the environment in order to accurately

establish threshold values.

Based on

baseline

values

Based on

baseline

values

In case the reported values exceed the baseline

response time constantly, a potential

performance issue needs to be investigated at

the SQL server level.

Database Connected

Indicates whether this service is in contact with its

database. (1 is connected; 0 is not connected).

0 (for over

30 minutes)

Both values report connectivity issues of the

XenDesktop Broker service with the database. In

case issues are reported, SQL server and

network availability needs to be verified.

Database Transaction

Errors/sec

The rate at which database transactions are failing.

None

Both values report connectivity issues of the

XenDesktop Broker service with the database. In

case issues are reported, SQL server and

network availability needs to be verified.

Table 75: Recommended XenApp/XenDesktop Metrics

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StoreFront

These performance counters are specific to the StoreFront servers.

Metric

Description

Warning

(Yellow)

Critical

(Red)

Troubleshooting / Remediation

ASP.NET – Request

Queued

The number of requests waiting to be processed by

ASP. A baseline needs to be established in the

environment in order to accurately establish

threshold values.

Based on

baseline

values

Based on

baseline

values

In case the queue length exceeds the critical

limit requests may be rejected. In this case it

should be considered to add additional

StoreFront or Web Interface servers to the load

balancing team in order to distribute the load

across more nodes.

ASP.NET – Requests

Rejected

The number of requests rejected because the request

queue was full.

None

>=1

When this limit is exceeded, requests will be

rejected with a 503 status code and the

message "Server is too busy." Please follow the

steps outlined for counter “ASP.NET – Request

Queued”

APP_POOL_WAS\Cur

rent Application Pool

State\Citrix Receiver

for Web

A value of 5 indicates the Application Pool is

stopped and Receiver for Web will display an

error.

APP_POOL_WAS\Cur

rent Application Pool

State\Citrix Delivery

Services

Authentication

A value of 5 indicates the Application Pool is

stopped and StoreFront Authentication will not

be successful.

APP_POOL_WAS\Cur

rent Application Pool

State\Citrix Delivery

Services Resource

A value of 5 indicates the Application Pool is

stopped.

Request response

regardless it is authentication, enumerate or

subscription) should be 3 to 5 seconds

(http://www.perftestplus.com/resources/how_fast.pd

Table 76: Recommended StoreFront/Web Interface Metrics

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Citrix License Server

These performance counters are specific to the Citrix License Server.

Metric

Description

Warning

(Yellow)

Critical

(Red)

Troubleshooting / Remediation

Citrix Licensing – Last

Recorded License

Check-Out Response

Time

Displays the last recorded license check-out response

time in milliseconds.

>2000 ms

> 5000 ms

If the reported values exceed the 5000 ms

response time, a potential performance issue

needs to be investigated in the Citrix License

Server.

Citrix Licensing –

License Server

Connection Failure

Displays the number of minutes that XenDesktop has

been disconnected from the License Server.

> 1 minute

> 1440

minutes

Both values report connectivity issues with the

License Server. In case issues are reported,

License Server and network availability needs to

be verified.

Table 77: Recommended Citrix License Server Metrics

Decision: Services Monitoring

Windows services that are critical to basic server functionality should be automatically monitored to ensure that they are running properly. The

following table provides a list of the common Windows services that should be monitored. When any of these services are restarted or stopped a

warning (Yellow) or critical (Red) alert should be assigned respectively. The recommended recovery actions for the services listed below are as

follows:

 First failure: Restart the Service

 Second Failure: Restart the Service

 Subsequent Failures: Put the server in maintenance mode and investigate the root cause

XenApp/XenDesktop

Service

Functionality

Administration Risk

Citrix AD Identity

Service

Manages Active Directory computer accounts.

Dependencies:

 WMI Service

Machine Creation Service relies on this service to create virtual machines.

Administrators will be unable to create new or modify existing Machine

Catalogs. Administrators will be unable to establish new connections to

Citrix Studio.

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Citrix Broker

Service

Manages connections to virtual machines and applications.

If this service is stopped administrators will be unable to make changes to

the environment or establish new connections to Citrix Studio. Any existing

administrator connections to Citrix Studio can also be terminated.

If this service is stopped existing user connections are not affected. No new

connections can be established. Users logging into StoreFront will be unable

to see any resources available for selection. Once the service is restarted

users will need to re-login to StoreFront to establish connections.

Citrix

Configuration

Logging Service

Logs administrator activity and configuration changes in a

XenDesktop deployment.

If this service is stopped XenApp/XenDesktop will be unable to

communicate with the Configuration Logging Database. Administrators will

be unable make changes to the environment or establish new connections

to Citrix Studio.

Citrix

Configuration

Service

Stores service configuration information.

Dependencies:

 WMI Service

If this service is stopped administrators will be unable to make changes to

the environment or establish new connections to Citrix Studio.

Citrix Delegated

Administration

Service

Manages configuration of delegated administration

permissions.

If this service is stopped XenApp/XenDesktop cannot assign administrative

permissions. Administrators will be unable to make changes to the

environment or establish new connections to Citrix Studio. Administrators

will be unable to establish new connections to Citrix Director and existing

sessions within Citrix Director will be interrupted.

Citrix Diagnostic

Facility COM

Server Service

Manages and controls Citrix diagnostic trace sessions on the

system.

Dependencies:

 RPC Service

This service has no impact on the production environment. It is used to

generate CDF trace files which aid in troubleshooting issues.

Citrix

Environment

Test Service

Manages tests for evaluating the state of a XenDesktop Site.

If this service is stopped administrators will be unable to establish new

connections to Citrix Studio. Administrators will also be unable to check the

status of the Citrix site configuration, machine catalogs, and delivery groups

by running the tests under “Common Tasks” in the Citrix Studio

administration console.

Citrix Host

Services

Manages host and hypervisor connections.

Dependencies:

 WMI Service

Administrators will be unable to create new Machine Catalogs or control

virtual machine power settings via Citrix Studio. Administrators will be

unable to establish new connections to Citrix Studio.

Users may experience issues connecting to virtual desktops when this service

is not available. If this service is stopped existing connections are not

affected.

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Citrix Machine

Creation Service

Creates new virtual machines.

Dependencies:

 WMI Service

Administrators will be unable to create new or modify existing Machine

Catalogs or establish new connections to Citrix Studio. Administrators will be

unable to establish new connections to Citrix Studio.

Citrix Monitor

Service

Monitors the FlexCast system.

If this service is stopped XenApp/XenDesktop will be unable to

communicate with the Monitoring Database. Citrix Director will be unable to

retrieve any data on the environment. Administrators will be unable to

establish new connections to Citrix Studio.

Citrix StoreFront

Service

Manages deployment of StoreFront.

Administrators will be unable to establish new connections to Citrix Studio.

Table 78: XenApp/XenDesktop 7.x Services

Delivery Controller Services Monitoring in Citrix Director

The Infrastructure pane within the Citrix Director dashboard provides status of the services running on the Delivery Controllers and will provide

warning indications if a service or Controller is unavailable. These alerts can be accessed by clicking the Alert hyperlink within the Infrastructure

pane.

Figure 44: Citrix Director Infrastructure Pane

Provisioning Services

Service

Functionality

Risk

Citrix PVS PXE

Service

Provides the PVS PXE Boot Server functionality.

Note: Only applicable when PXE boot is used.

On failure of this service target devices may not be able to boot successfully

if PXE booting is leveraged.

Citrix PVS Stream

Service

Streams contents of the vDisk to the target device on

demand.

If this service stopped it will not be possible to stream vDisk images.

Citrix PVS SOAP

Service

Provides framework for external or existing solutions to

interface with Provisioning services.

Note: Only impacts console operations. User is unaffected

If this service fails PVS Server to PVS Server communication as well as PVS

Console to PVS Server communication is not possible.

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Citrix PVS TFTP

Service

Provides the TFTP Server functionality.

Note: Only applicable when TFTP is used.

On failure of this service target devices may not be able to boot if this server

is used as TFTP server for the bootstrap.

Citrix PVS Two-

Stage Boot

Service

Provides the bootstrap functionality for devices booting by

means of a BDM ISO file.

Note: Only when BDM boot partitions are used.

On failure of this service target devices may not be able to boot if a BDM ISO

file is used.

Table 79: Provisioning Server Services

StoreFront

Service

Functionality

Risk

Citrix Cluster Join

Service

Provides Server Group join services.

This service is started when adding additional StoreFront servers to a Server

Group. If this service does not start or is interrupted when this process is

initiated the additional server will be unable to join the indicated Server

Group and the process will result in an error.

Citrix

Configuration

Replication

Provides access to Delivery Services configuration

information.

This service only exists on the primary StoreFront server of a Server Group. If

this service is stopped additional StoreFront servers will be unable to join the

Server Group and any changes made to the primary StoreFront server will

not be replicated to other servers. This can result in servers within the Server

Group being out of sync.

Citrix Credential

Wallet

Provides a secure store of credentials.

Dependencies:

 Citrix Peer Resolution Service

If this service is stopped users will be unable to login to access their desktops

or applications. Users logged into StoreFront will be unable to launch new

application or desktop sessions. Existing application or desktop sessions are

unaffected.

Citrix Default

Domain Services

Provides authentication, change password, and other

domain services.

If this service is stopped users will be unable to login to access their desktops

or applications. Users currently logged in will not be affected.

Citrix Peer

Resolution

Service

Resolves peer names within peer-to-peer meshes.

On failure of this service both the Citrix Credential Wallet and Citrix

Subscriptions store are stopped generating the risks associated with those

services.

Citrix Storefront

Privileged

Administration

Service

Manages privileged operations on Storefront

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Citrix

Subscriptions

Store

Provides a store and replication of user subscriptions.

Dependencies:

 Citrix Peer Resolution Service

If this service is stopped Citrix Receiver cannot add, remove, and reposition

applications within StoreFront. Users will need to re-add applications and all

changes made to their selection of applications within the StoreFront store

will not be saved or replicated to other sessions. Original user configuration

will be restored once the service is restarted.

World Wide

Web Publishing

Service

Provides web connectivity and administration through the

Internet Information Services Manager.

Dependencies:

 HTTP

 RPC Service

Access to published applications or published desktops will not be available

through StoreFront. Users will be unable to resolve the Receiver for Web

application or desktop sessions and will need to reenter credentials when

the service is restarted. Existing application or desktop sessions are

unaffected.

Table 80: StoreFront Services

Web Interface

Service

Functionality

Risk

World Wide

Web Publishing

Service

Provides web connectivity and administration through the

Internet Information Services Manager.

Dependencies:

 HTTP

 RPC Service

Access to published applications or published desktops will not be available

through Web Interface if the WWW service is not available.

Table 81: Web Interface Services

Citrix License Server

Service

Functionality

Risk

Citrix Licensing

Service

Provides licensing services for Citrix products.

Licensing mode changes to grace period when service is stopped or License

Server cannot be contacted. If not monitored, functionality of Citrix products

will cease after grace period expires.

Citrix Licensing

Support Service

This account controls reading the license files and updating

strings with license trailers (data dictionary functionality).

None

Citrix Licensing

WMI

The Citrix License Management Console collects license data

information using the WMI service.

None

Table 82: Citrix License Server Service

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Decision: Events Monitoring

Monitoring the Windows Event Log for unknown or critical events can help to proactively discover

issues and allow administrators to understand event patterns:

 Licensing - Errors in the Event Log dealing with Remote Desktop licensing should be

investigated. This might be a result of the installed Citrix product not being able to contact

the Remote Desktop Licensing Server or the Citrix Licensing Server. If errors in the Event Log

are not reviewed, users might eventually be denied access because they cannot acquire a

valid license.

 Hardware Failure - Any event notification that relates to a hardware failure should be

looked at immediately. Any device that has failed will have an impact on the performance of

the system. At a minimum, a hardware failure will remove the redundancy of the

component.

 Security Warnings - Customers should investigate security warnings or audit failure events

regarding failed logons in the security log. This could be an indication that someone is

attempting to compromise the servers.

 Disk Capacity - As the drives of a Windows system reach 90% of capacity, an event error

message will be generated. To ensure continuous service, customers should poll these

event errors. As the system runs out of hard disk space, the system is put at severe risk. The

server might not have enough space left to service the requests of users for temporary file

storage.

 Application / Service errors - Any event notification that relates to application or services

errors should be investigated.

 Citrix errors - All Citrix software components will leverage the Windows Event Log for error

logging. A list of the known Event Log warnings and errors issued by Citrix components can

be found at the following links:

o Event Codes Generated by PVS

o XenDesktop 7 - Event Log Messages

It is important to periodically check the Event Viewer for Citrix related warnings or errors.

Warnings or errors that repeatedly appear in the logs should be investigated immediately,

because it may indicate a problem that could severely impact the Citrix environment if not

properly resolved.

In multi-server environments it becomes easier to administer the servers when logs can be collected

and reviewed from a central location. Most enterprise grade monitoring solutions provide this

functionality. More sophisticated monitoring solutions enable an administrator to correlate event

information with other data points such as performance metrics or availability statistics. In case the

selected monitoring solution does not provide this functionality the Windows Server 2008 R2 or

Windows Server 2012/2012 R2 Event Log subscription feature can be used. This feature allows

administrators to receive events from multiple servers and view them from a designated collector

computer. Please see Microsoft TechNet article Manage Subscriptions for more information.

XenServer is also capable of sending its logs to a central syslog server. The administrator sets the IP

address of the syslog daemon server in the properties of each XenServer in the pool. This

configuration allows administrators to capture real-time activity across multiple XenServer hosts.

Further information can be found within the XenServer Admin Guide.

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Decision: Capacity Management

In addition to the day-to-day monitoring of system-level metrics, performance metrics should be

tracked from a historical perspective to help plan for future growth as more users access the

environment.

A baseline of the environment performance should be taken so that it can be compared against

performance over time. For example, if a user complains of poor performance, this baseline can be

used for comparison purposes to identify if the issues are related to the user load exceeding the

capacity of the environment.

An example of baseline performance metrics for capacity management would include historical

data for CPU, Memory, and network utilization on the Delivery Controller and application servers or

desktops.

Citrix Director

Administrators can utilize the Trends view within Citrix Director to track different parameters of

the Citrix XenApp/XenDesktop deployment over time. These parameters can be leveraged for

capacity planning of the Citrix environment.

From the Trends view, administrators can see historical data that is broken up into several

categories including:

 Sessions - Provides the concurrent session usage over time enabling the ability to size

the environment appropriately.

 Connection Failures - Gives an overview of the different types of connection failures that

have occurred across different Delivery Groups.

 Failed Desktop OS Machines – Gives an overview of the different problems associated

with failures in desktop machines.

 Failed Server OS Machines - Gives an overview of the different problems associated with

failures in server machines.

 Logon Performance – Shows how long it takes for users to log on to their applications

and desktops.

 Load Evaluator Index – Provides various performance counter-based metrics, including

CPU, Memory, and Disk Usage for Server OS machines.

 Capacity Management – Shows utilization of published applications and desktops

 Resource Utilization – Provides information on CPU, Memory and storage resource

utilization

 Custom Reports – Allows administrators to create custom historical reports on

numerous metrics captured by the system.

 Hosted Application Usage – Details all applications published in the site and can provide

usage information about each individual applications in detail (concurrent instances,

launches, usage duration, and so on).

Note: Requires XenApp or XenDesktop Platinum licensing

 Network – Network analytics provided through NetScaler HDX Insight.

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Figure 45: Citrix Director Trends View

For more information on Citrix Director Trends, please refer to the following.

 Citrix Blogs – Citrix Director: Trends Explained

 Citrix Support – CTX139382 Best Practices for Citrix Director

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Acknowledgments

The creation of the handbook is a time consuming process and requires real deployment experience

across many scenarios. Citrix would like to thank the authors and subject matter experts who contributed

to the Citrix VDI Handbook.

Authors

Name

Title

Daniel Feller

Lead Architect

Nicholas Rintalan

Lead Architect

Jeff Qiu

Architect

Matthew Brooks

Sr. TechProduct Marketing Manager

Andy Baker

Senior Architect

Thomas Berger

Sr. Product Marketing Manager

Amit Ben-Chanoch

Technical Product Manager

Rich Meesters

Architect

Roger LaMarca

Principal Consultant

Adeel Arshed

Sr. Consultant

Rafael Jose Gomez

Consultant

Ed Duncan

Consultant

Kevin Nardone

Principal Consultant

Subject Matter Experts

Name

Title

Brendan Lin

Sr. Architect

Sarah Steinhoff

Sr. Architect

Dan Morgan

Principal Consultant

Diego Madiedo

Architect

Cid Neves

Sr. Architect

Michael Havens

Principal Consultant

Ryan Robott

Josh Fu

Maria Chang

Senior Consultant

Pablo Legorreta

Architect

Uzair Ali

Principal Consultant

Steven Kruger

Lead Systems Engineer

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Revision History

Revision

Change Description

Updated By

Date

1.0

XD7.6 LTSR Handbook Released

Daniel Feller

(Lead Architect)

September

30, 2016

1.1

Minor grammatical changes throughout handbook

Daniel Feller

(Lead Architect)

November 9,

2016

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2.0

Updates for XenApp/XenDesktop LTSR 7.15

Updates:

 Assess - Define the Organization requirements

 Assess - VDI Models

 Design - User Layer - Receiver - Updates

 Design - Resource - Applications - App Delivery

Method

 Design - Resource - VM - Virtual Processor

 Design - Resource - VM - Virtual Memory

 Design - Resource - VM - Disk Cache

 Design - Resource - VM - RAM Cache

 Design - Resource - VM - Storage IOPS

 Design - Resource - VM – GPU

 Design – Control – PVS – Bootstrap Delivery

 Design – Hardware – Physical Processor (pCPU)

 Design – Hardware – Physical Memory (pRAM)

 Design – Hardware – GPU

 Monitor – Support – Certifications and Training

Additions:

 Design - Layer 0 - Conceptual Architecture

 Design – Layer 0 – Conceptual Architecture –

Delivery Model

 Design – Layer 0 – Conceptual Architecture – Site

Topology

 Design – Layer 0 – Conceptual Architecture –

Image Management Strategy

 Design - User Layer – Unified Endpoint

Management (UEM)

 Design - Access - Authentication - Authentication

Provider

 Design - Access - StoreFront - Aggregation

Groups

 Design – Access – Site-to-Site

 Design – Access – Site-to-Site – HDX Optimized

Routing

 Design – Access – Site-to-Site – Virtual WAN

 Design - Resource - User Experience – Display

Protocol

 Design - Resource - User Experience – Transport

Protocol

 Design - Resource - User Experience – Logon

Optimization

 Design - Resource - User Experience – User Self

Service

 Design - Resource - User Data – Data Location

 Design - Resource - User Data – Data Access

 Design - Resource - User Data – Data Recovery

 Design - Resource - VM - CPU Optimization

 Design - Resource - VM - RAM Optimization

 Design - Resource - VM - IO Prioritization

 Design - Control - Delivery Controller - Local

Host Cache

Daniel Feller

(Lead Workspace Architect)

Jeff Qiu

(Architect)

Matthew Brooks (Sr. Tech

Product Marketing Manager)

August 12,

2017

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 Design – Control – Cloud Connector

 Design – Control – Cloud Connector – Server

Sizing

 Design – Control – PVS – Read Cache (PVS

Accelerator)

 Design – Control – MCS

 Design – Control – MCS – Storage Location

 Design – Control – MCS – Cloning Type

 Design – Control – MCS – Read Cache

 Design – Control – MCS – Write Cache

 Monitor – Monitoring – Automated Monitoring

Deletions:

 Design - Control - Database - Connection

Leasing

2.01

Updates

 Assess – Define User Group – Assign VDI Models

(Linux app definition)

Daniel Feller

(Lead Workspace Architect)

August 29,

2007

2.02

Updates

 Design – Conceptual – Site Topology (corrected

table header)

Daniel Feller

(Lead Workspace Architect)

August 30,

2017