XenDesktop Storage Planning Guide - Optimize Performance

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XenDesktop Planning Guide
Storage Best Practices

Contents
Overview.............................................................................................................................................................3
Guidelines ...........................................................................................................................................................4
Organizational Requirements........................................................................................................................................4
Technical Requirements.................................................................................................................................................5
Performance Requirements...........................................................................................................................................................5
Functional Requirements...............................................................................................................................................................8
Avoid Bottlenecks...........................................................................................................................................................................9
High Availability............................................................................................................................................................................10
File System Alignment .................................................................................................................................................................11
Validate and Monitor....................................................................................................................................................................11
Planning.............................................................................................................................................................12
Choosing the appropriate RAID Level.....................................................................................................................12
Number of Disks (IOPS) ............................................................................................................................................13
Caching...........................................................................................................................................................................13
Connectivity...................................................................................................................................................................14
Provisioning Services ...................................................................................................................................................14
XenDesktop – Machine Creation Services...............................................................................................................16
XenServer.......................................................................................................................................................................17
Appendix...........................................................................................................................................................19

Overview
The Citrix Storage planning guide provides a list of best practices, recommendations and
performance related tips that cover the most critical areas of storage integration with Citrix
XenDesktop. It is not intended as a comprehensive guide for planning and configuring storage
infrastructures, nor as a storage training handbook.
Due to scope, this guide provides some device-specific information. For additional device- specific
configuration, Citrix suggests reviewing the storage vendor’s documentation, the storage vendor’s
hardware compatibility list, and contacting the vendor’s technical support if necessary.
The following provides a non-comprehensive list of available vendor specific reference architectures
and best practice guides, which are highly recommended:
 Citrix XenServer and NetApp Storage Best Practices
 DR Solution for XenDesktop on NetApp
 EMC Infrastructure for Virtual Desktops
 HP Converged Infrastructure enterprise reference architecture for client virtualization
 Dell Virtual Remote Desktop Solution Reference Architecture
 Cisco Validated Design

Guidelines
The initial step in order to plan a storage infrastructure is –as with any other planning process– to
assess and to understand the specific storage needs of an organization. Those needs consist of
organizational as well as technical requirements, which are discussed within this section. While this
section does discuss how to plan for and work with various storage architectures and technologies, it
is not possible to provide architectural blueprints because of the wide variety of storage systems and
technologies available on the market. Therefore it is strongly recommended to involve storage
vendors or specialized partners in the planning process.
Organizational Requirements
Organizational storage requirements go beyond having sufficient capacity for the data stored on
each server and workstation. The following provides a non-exclusive list of items for
consideration:
 Does it align with IT strategy? In general, storage planning should fully align with a
company’s IT strategy, in terms of preferred storage vendor / partner, budget, anticipated
growth, and expected new workloads or applications.
 Can data be consolidated or existing storage infrastructures be leveraged?
Consolidating storage or leveraging existing systems reduces the cost of managing storage
on multiple systems and increases the efficiency of storage allocation and backup tasks.
However, consolidation also introduces risk, because more applications, workloads and
users depend on fewer systems; so an outage has a greater impact than in a more
distributed installation. If it is planned to consolidate storage, it might be necessary to
investigate ways to increase storage availability. It is important to understand that besides
disk space storage performance (latency , IOPS) and the respective impact when adding
additional systems is a vital criteria when consolidating storage. Especially in VDI
environments this is underestimated in many cases.
 Is high availability required and how long can data recovery take? Some critical
systems must be continuously available. For example, it might require that the systems
experience zero downtime. Other workloads might be able to tolerate a one-hour window
of downtime. Planning needs to take into account the organization’s as well as workload
or application specific tolerance for downtime during data recovery.
 Will other systems / infrastructures be influenced? Depending on the size and setup
of a storage system, it can influence other systems or infrastructures. For example, when
planning for data replication, the utilization of the LAN or the WAN in between the data
centers will increase and it could therefore introduce latency for other systems that rely
on the same communication paths.

 Which level of storage expertise exists? Planning as well as subsequent operations may
require special knowledge, especially when storage solutions with a high degree of
complexity or with complex management interfaces will be implemented. It is important
to assess existing knowledge, possible synergies and to understand training needs when
introducing a new storage infrastructure.
Technical Requirements
Determining the technical requirements can be very a complex procedure, mainly depending on
the amount and complexity of the applications and workloads which will be connected to the
storage infrastructure. In order to keep this guide focused, only two aspects (performance and
functionality) for Citrix related workloads will be considered.
Performance Requirements
Understanding the I/O characteristics and performance requirements of an application or
workload is vital in order to be successful in designing and deploying a scalable storage
infrastructure which meets the performance expectations of the business. Important data points
that should be measured for all storage dependent applications and workloads include:
 Typical I/O rates
(I/O’s per second (IOPS), IO size (request size), MB/s (throughput))
 Read and Write ratio
 Sequential vs. Random I/O ratio  For XenApp and XenDesktop systems, typically all
I/O will be random. Sequential IO is generated by databases or other high data volume
applications only
Note: The following resources provide information about typical I/O characteristics for virtual
desktop environments (for reference purposes only):
 http://blogs.citrix.com/2011/06/07/iops-in-the-real-world
 http://www.jimmoyle.com/2011/05/windows-7-iops-for-vdi-deep-dive

Using Windows, these data points can be gathered by means of the built-in Performance
Monitor, which offers the ability to track the following counters (object Physical Disk):
Information
about
Read counter Write counter Combined counter
IOPS Disk Reads/sec Disk Writes/sec Disk Transfers/sec
I/O size Avg. Disk Bytes/Read Avg. Disk Bytes/Write Avg. Disk Bytes/Transfer
By using the results of these counters the following equations help to determine the missing
pieces of information:
 Throughput: Disk Transfers/sec * Avg. Disk Bytes/Transfer
 % of reads: (Disk Reads/sec * 100) / Disk Transfers/sec
 % of writes: (Disk Writes/sec * 100) / Disk Transfers/sec
Performance Monitor also exposes similar counters per process in order to gather performance
related information at an application level rather than at a machine level. Alternatively the
Windows built-in Resource Monitor as well as the SysInternals Process Monitor or other 3rd
party
tools (i.e. hIOmon) provide similar data.

Using XenServer or other Linux based operating systems, these data points can be gathered by
means of the iostat command. In order to run at a regular interval, over a certain period of time
and to capture the output in a format that can be imported to Excel, it is necessary to run iostat
as follows:
iostat -xk 15 5760 | awk 'BEGIN {print "Time Device rrqm/s wrqm/s r/s w/s rkB/s wkB/s
avgrq-sz avgqu-sz await svctm %util"} /sda1/ {print strftime("%H:%M:%S"),$0}' >iostat.csv &
The command is comprised of the following parameters, which may need to be modified for
every environment:
Parameter Meaning
iostat –xk 15 5760 Runs iostat with extended statistics (in KB format) at a 15 second
interval 5760 times (= 24 hours)
/sda1/ Filters the output for block device sda1
>iostat.csv Writes the iostat output into the file iostat.csv
& Runs in the background to free up the shell console for other
commands
By using iostat the following counters can be tracked:
Information
about
Read counter Write counter
IOPS r/s w/s
I/O size rkB/s wkB/s
By using the results of these counters, the following equations help to determine the missing
pieces of information:
 Throughput: rkB/s + wkB/s
 % of reads:
 % of writes:
By using XenTop on a XenServer host, the aforementioned counters can be obtained on a per
virtual machine basis. Please refer to the Appendix of this document for further information.

Functional Requirements
Determining the functional requirements is basically a balancing act between the prerequisites of
a workload or application and the technical capabilities of any given storage architecture or
storage protocol. The following table outlines this procedure for the current versions of
Provisioning Services (PVS. Further information can be found within the planning section of this
document.
Protocol /
Functionality
CIFS NFS iSCSI FC
PVS – central vDisk
management
X X (X)1
(X)1
PVS – caching of
vDisks
(X)2 X X X
1: Additional software (clustered file system) required
2: Opportunistic Locking configuration of Windows needs to be changed. Please refer to the
Appendix of this document for further information.

Avoid Bottlenecks
Most applications and workloads are very sensitive with regards to the latency of storage I/O
operations. For example within virtual desktop environments, high I/O latency negatively
impacts the user experience. It is vital to avoid bottlenecks within the storage infrastructure.
 Networking: In scenarios with congested network interfaces or links, data packets may be
dropped. This can severely impact storage traffic based on standard Ethernet, such as CIFS,
NFS, iSCSI or FCoE as dropped packets have to be retransmitted, which adds latency to
the storage I/O operation. For shared interfaces (e.g. Blade Chassis uplinks or Host NICs)
or central network links (e.g. inter-switch, inter-data center) oversubscription scenarios are
likely. While VLANs allow logical separation of network traffic at layer 2 of the OSI model,
they provide no mechanism to allow oversubscription of physical links; a 10GBit/s link has
a maximum of 10Gbit/s no matter how many VLANs are configured. It is therefore a best
practice to dedicate network interfaces and links for applications and workloads with very
high I/O requirements. For maximum performance and reliability, a fully dedicated, non-
shared network infrastructure is recommended for all storage protocols which leverage
standard networking technologies.
 SAN Fabric. While a dedicated SAN Fabric, which relies on Fibre Channel rather than
Ethernet based communication, is typically a continuously monitored, optimized and
lossless network for storage traffic, it potentially can imply the same risks as described
within the networking section.
 Storage Hardware: In multi-tenant (or other shared) scenarios with unpredictable data
access patterns, Storage Processors, NAS heads or other shared hardware such as switches
or HBAs can become a bottleneck. Proactive monitoring as well as trend and capacity
planning are imperative. Furthermore, it is a best practice to leverage all available paths and
storage controllers to distribute the load across all available resources. For large
environments with unpredictable high volume data traffic, dedicating the storage
infrastructure for virtual desktops can become the preferred option, in order to keep data
latency consistently on the lowest level possible.
 Spindles: Avoid hosting multiple workloads with high I/O characteristics on the same set
of disk spindles concurrently. Furthermore, it is a good practice to “have an adequate
number of spindles to support your I/O requirements with an acceptable latency.”1
1
http://technet.microsoft.com/en-us/library/cc966534.aspx

 RAID levels. The RAID level of a storage sub-system can have a direct impact on the
performance of the applications and workloads attached to this particular storage. While
some RAID levels are optimized for writes (i.e. RAID 0, 1, 10) others such as RAID 5 or 6
are not (which can multiply the storage utilization performance wise by a factor 4 or 6 (write
penalty)). Therefore, it is best practice to configure the RAID level (whenever possible)
based on the I/O pattern of the related applications and workloads.
High Availability
It is a best practice to implement all storage related components in a highly available manner.
This includes HBAs or NICs, network paths, storage controllers and disk shelves. The following
diagram outlines a sample HA configuration for an iSCSI based storage attached to a XenServer:
In the environment shown above, XenServer MultiPathing allows storage I/O to leverage
multiple redundant network paths to the storage infrastructure, which can increase performance
and provide high availability. Once again, the storage array must support this configuration. As
previously discussed, this diagram shows a dedicated, isolated switch and network infrastructure
for storage traffic.

File System Alignment
In order to minimize the utilization of the storage sub-systems, it is best practice to fully align the
file systems at all layers (i.e. VM, Hypervisor, Storage). “For optimal performance, the starting
offset of a file system should align with the start of a block in the next lower layer of storage. For
example, an NTFS file system that resides on a LUN should have an offset that is divisible by the
block size or stripe size of the storage array presenting the LUN. Misalignment of block
boundaries at any one of these storage layers can result in performance degradation as multiple
storage I/O operations can be required to access a single block of data.”2
Please note that while Windows 7 and Windows Server 2008 or above should automatically align
disk partitions correctly, it is recommended to verify this for every new workload. The following
figure outlines a misalignment scenario for a Windows XP NTFS partition.
Validate and Monitor
Validating the storage infrastructure prior to deployment in production is essential in order to
isolate and address potential I/O bottlenecks, optimize throughput and to tune all components
which sit in the data path including HBA’s, disk controllers, device cache, storage processors,
disks, RAID levels, and where applicable, network and SAN fabric components. Subsequent
monitoring is also essential to ensure that performance levels are being maintained in line with
agreed service levels and to provide data which his useful for scalability analysis and capacity
planning. Testing and monitoring processes should include at the very least:
 Optimization and rationalization of firmware versions for all storage components
 Storage I/O path utilization
 Utilization of the storage controller / NAS Head
 Read versus Write I/O distribution
 Cache hit rates and utilization
 Utilization of the disk spindles (performance / avail. space)
 Throughput, latency and queue depth
2
http://media.netapp.com/documents/tr-3747.pdf

Planning
Planning a storage infrastructure is a highly individual task, which, as outlined earlier, depends on
technical as well as unique organizational criteria. It is recommended to involve a storage vendor or
a partner in the early phases of a storage design initiative in order to achieve the best aligned storage
design. Nevertheless, this section will provide guidance for planning a storage infrastructure.
Choosing the appropriate 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 intense workloads, RAID levels that are optimized for read
operations, such as RAID 0, 1, 5 10, are optimal. This is because these RAID levels allow read
operations to be spread across all disks within the RAID set simultaneously.
For hosting write intense workloads, such as Provisioning Services Write Cache and Machine
Creation Services differencing disks, RAID levels such as RAID 0, 10 are optimal, as these are
optimized for writes or have a low write penalty.
The following table outlines the key quantitative attributes of the most commonly used RAID
levels:
RAID
Level
Capacity Fault
Tolerance
Read Performance
(random)
Write Performance
(random)
0 100% None Very Good Very Good
(Write Penalty 0)
1 50% Good Very Good Good
(Write Penalty 2)
5 Disk size *
(# of disks -1)
Good Very Good Bad
(Write Penalty 4)
10 50% Very Good Very Good Good
(Write Penalty 2)
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”3
as outlined within the example below (calculating RAID5 parity during a write / without
optimization technologies):
1) Read the old data
2) Read the old parity and calculate the difference between old data and new data, and old parity and new parity
3) Write the new data
4) Write the new parity
3
http://www.snia.org/education/dictionary/w

Number of Disks (IOPS)
To determine the number of disks required, from a performance point of view, 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 following examples outline the
necessary calculations.
The basic calculation is:
The following table provides examples of how many disks are required for the given scenarios.
RAID Level RAW IOPS
(per disk)
Workload
IOPS
Read % Write % Disks
Count
RAID 0 175 2000 20% 80% 12
175 2000 80% 20% 12
RAID 1/10 175 2000 20% 80% 21
175 2000 80% 20% 14
RAID 5 175 2000 20% 80% 39
175 2000 80% 20% 19
Caching
In order to achieve the IOPS required with the least number of disks and to mitigate peak load
scenarios, caching techniques are provided by the vendors at various levels within the storage
stack. The read/write ratio of a workload determines the required caching configuration, as
outlined below:
Workload Read Cache Write Cache
MCS LUN 50% 50%
PVS Write Cache - 100%
XenDesktop
(installed)
- 100%
XenApp
(installed)
- 100%

Connectivity
Storage subsystems can be attached to one or many computer systems by means of various
protocols, such as NFS, iSCSI or Fibre Channel. Determining the functional requirements of an
application or workload and matching this with the individual capabilities of a storage protocol
are of the same importance during the planning phase as considering high availability and
throughput. As discussed earlier, it is general best practice to use MultiPathing or automatic fail-
over techniques, for storage paths.
In order to plan for the required throughput, it is necessary to sum up the throughputs for every
individual system that uses a shared component or network path. Following an example for an
environment with 100 similar virtual machines (hosted on 10 virtualization hosts and connected
to one NAS head) is provided:
Average Peak
Throughput per VM 10 Mbps 30 Mbps
Throughput per Host 100 Mbps
(10 VMs*10Mbps)
300 Mbps
(10 VMs*30Mbps)
Throughput for
Storage
1 Gbps
(10 Hosts*100 Mbps)
3 Gbps
(10 Hosts*300 Mbps)
The NIC used for storage communication needs to be a 1 Gbit/s adapter in order to cope with
the peak load.
The NAS head as well as its network connection need to support 3 GBit/s worth of data traffic,
in order to support the peak load of all systems.
Provisioning Services
While a Citrix Provisioning Server itself is a standard Windows Server, it still has some specific
requirements when it comes to storage integration. The following items outline the common best
practices.
vDisk Storage
In most cases, vDisks are used in read-only mode (standard) where multiple target devices
simultaneously access a single vDisk. Therefore the following best practices focus on standard mode
scenarios only.
 Storage Protocol and Caching: In order to enable the Windows Server 2008 R2
(recommended OS) to cache parts of the actively streamed vDisks in memory, it is
important to either

o Locate the vDisk Store on a block level storage device. Block level storage devices
are local disks, or iSCSI / Fibre Channel attached LUNs.
o Locate the vDisk on a NFS or CIFS share and modify the Opportunistic Locking
configuration of Windows. Please refer to the Appendix of this document for further
information.
Note: In case the CIFS protocol is used to access the vDisks, it is strongly
recommended to leverage SMB 2.x whenever possible. Please refer to the Appendix
of this document for further information.
Note: Citrix recommends Windows Server 2008 R2 as platform for Provisioning Services
due to the improved caching mechanisms and the ability to address large amounts of
memory. To allow Windows to cache vDisks effectively, a minimum of 2GB RAM per
active vDisk (XenDesktop) or 4GB RAM per active vDisk (XenApp) should be configured
in addition to 2GB for the OS itself.
 I/O Pattern: Standard mode vDisks are accessed by the Provisioning Servers with an
almost 100% random read I/O pattern (except during maintenance). Because of the caching
mechanisms of Windows, which were described earlier, vDisks will be read into free
memory and the storage utilization will drop significantly.
 Availability: Although certain parts of active vDisks can be cached in memory, the vDisk
files must be available at all times. Therefore, vDisk stores need to be hosted on highly
available storage sub-systems (local or shared). This is especially true in scenarios with a
shared vDisk store (i.e. via CIFS / NFS), where high availability is vital.
Write Cache Storage
 I/O Pattern: The write cache holds all writes from a PVS target device and has a mixed
I/O pattern depending on the status and the uptime of an individual target. Over time, the
probability that items will be read from the write cache will increase. In general a read/write
ratio of 5/95 or 20/80 for the write cache is expected. All I/Os are random. The storage
sub-system used for Write Cache storage should be optimized accordingly.
 Target Device RAM: All read and write operations on a Provisioning Services target
device will also get cached in the system cache memory of the target device. This includes
files read from PVS and file data written to the write cache. It is important to ensure that
your Windows targets have enough memory for adequate Windows file caching so that re-
reads are reduced.

XenDesktop – Machine Creation Services
While the Machine Creation Services feature of XenDesktop 5 has no direct integration with storage
sub-systems, it still has certain specific requirements, which are listed below:
 Thin Provisioning: The functionality of Machine Creation Services is comparable with a
linked-clone approach, although it allows the clones to be non-persistent in addition to the
common persistent only option. In order to minimize the storage space required for the
clones, Thin Provisioning and automatic disk space reclamation is required. With regard to a
XenServer based environment, it is best practice to deploy Machine Creation Services using
NFS based storage repositories, which includes these features by default. Please refer to the
Appendix of this document for further information.
The following diagram illustrates the Thin Provisioning disk space savings:
 I/O Pattern. In general MCS based workloads have a random read/write I/O pattern. In
scenarios without IntelliCache the read/write ratio is expected to be 50/50 and the overall
IOPS are about 1.6 times higher than for Provisioning Services based workloads, as the
Provisioning Services vDisk caching mechanisms do not apply. For IntelliCache scenarios
with non-persistent desktops the read / write ratio observed at the shared storage will be
100% read, as all writes will be cached on the local hard disks of the XenServers. For
persistent desktops the read / write ratio will vary based on the fill level of the cache per
XenServer.

XenServer
The following items outline the common storage best practices for XenServer environments.
 Number of VMs per LUN: Storage LUNs that are connected to a XenServer using FC or
iSCSI may be represented as a single iSCSI queue on the storage side (storage dependent). In
the case where a LUN is shared among multiple virtual machines disks, all I/O has to
serialize through the iSCSI queue and only one virtual disk’s traffic can traverse the queue at
any point in time. This leaves all other virtual disks’ traffic waiting in line. Although it is
possible to parallelize iSCSI commands by implementing active/active MultiPathing or
optimizing the command traversal by techniques such as command batching, LUNs and
their respective iSCSI queue may become congested and the performance of the VMs may
decrease. Therefore it is a best practice to implement no more than 20-30 virtual machines
per LUN on average. The actual VM per LUN ratio is environment and workload specific
and needs to be determined by means of performance monitoring (i.e. VM specific
read/write latency) and with reference to the best practices of the storage vendor.
Note: This does not apply to NFS based shared storage, where tests have shown that even
with hundreds of VMs performance does not decline.
 Software Initiators: When using the XenServer’s built-in software iSCSI Initiator or the
NFS client, the network protocol processing takes place within the Control Domain of the
host system, which increases its CPU usage and memory footprint. In scenarios with a high
utilization of the host system, it is a best practice to implement hardware based iSCSI
Initiators or Network Interface Cards with TCP offloading capabilities.
Note: With the release of XenServer 5.6 FP1 the control domain (Dom0) is now equipped
with 4 vCPUs by default, which mitigates the risk of Dom0 congestion. For environments
with very high volume network traffic, it is best practice to configure IRQ Balancing. Please
refer to the Appendix of this document for further information.
 Bonding and MultiPathing. In general MultiPathing can leverage all available paths,
whereas bonding can use one active data path only. This is related to the SLB Load
Balancing algorithm, which is used for balancing data traffic for network bonds in
XenServer. The algorithm will assign one static data path (NIC) per VM and the XenServer
Control Domain (Dom0), which handles all I/O traffic, is seen as a single VM. Therefore it
is recommended to use MultiPathing wherever possible. Please refer to the Appendix of this
document for further information.

 Local Disk VM storage / IntelliCache: The functionality of IntelliCache, supported in
XenServer 5.6 FP1 and above, leverages the local XenServer disk subsystem to cache read
operations which originate from your NAS. Using the local disks of a server to cache read
and partially write requests of virtual machines can decrease the load seen on the shared
storage massively, but it dramatically increases the load on the local disks. To ensure the
local disks will not become a bottleneck with IntelliCache or other scenarios that make use
of local storage for VM disks, it is a best practice to closely monitor the disk utilization using
iostat or other monitoring tools. Furthermore, high performance disks (e.g. SAS 15k / SSD)
should be configured in a RAID level that is optimal for random reads and writes. In
addition it is highly recommended to equip storage array controllers with a minimum of
512MB read cache as well as (battery backed) write cache.

Appendix
The following items provide further insights into multiple topics discussed within this document:
 How to Use the XenServer Xentop Utility
http://support.citrix.com/article/CTX127896
 Why / How to modify Windows Opportunistic Locking:
http://blogs.citrix.com/2010/11/05/provisioning-services-and-cifs-stores-tuning-for-
performance
 Tuning CIFS / SMB for XenApp, Provisioning Services and File Servers
http://blogs.citrix.com/2010/10/21/smb-tuning-for-xenapp-and-file-servers-on-windows-
server-2008
 Advanced Memory and Storage Considerations for Provisioning Services
 IRQ Balancing: Distributing Guest Traffic Over Physical CPUs in XenServer
 Configuring iSCSI Multipathing Support for XenServer
 Using NFS for Machine Creation Services
http://blogs.citrix.com/2011/05/11/citrix-recommends-nfs-for-xendesktop-huh
 How to Use IntelliCache with XenDesktop
(http://support.citrix.com/article/CTX129052)
 Standard RAID levels explained
(http://en.wikipedia.org/wiki/Standard_RAID_levels)

Product Versions
Product Version
XenDesktop 5.0
XenServer 5.6
Provisioning Server 5.6
Revision History
Revision Change Description Updated By Date
1.0 Document created Thomas Berger – Architect
Gaby Hoffmann – Senior Consultant
Olivier Withoff – Architect
Peter David – Architect
Padraig Sweeney – Escalation Engineer
Christian Ferber – Systems Engineer
Martin Rowan – Director
Nicholas Rintalan – Sr. Architect
Dan Allen – Sr. Architect
Mark Nijmeijer – Director
Daniel Feller – Lead Architect
Tarkan Kocoglu – Director
August 12, 2011
About Citrix
Citrix Systems, Inc. (NASDAQ:CTXS) is the leading provider of virtualization, networking and software as a service
technologies for more than 230,000 organizations worldwide. Its Citrix Delivery Center, Citrix Cloud Center (C3)
and Citrix Online Services product families radically simplify computing for millions of users, delivering applications
as an on-demand service to any user, in any location on any device. Citrix customers include the world’s largest
Internet companies, 99 percent of Fortune Global 500 enterprises, and hundreds of thousands of small businesses
and prosumers worldwide. Citrix partners with over 10,000 companies worldwide in more than 100 countries.
Founded in 1989, annual revenue in 2010 was $1.9 billion.
©2011 Citrix Systems, Inc. All rights reserved. Citrix®, Access Gateway™, Branch Repeater™, Citrix Repeater™,
HDX™, XenServer™, XenApp™, XenDesktop™ and Citrix Delivery Center™ are trademarks of Citrix Systems, Inc.
and/or one or more of its subsidiaries, and may be registered in the United States Patent and Trademark Office
and in other countries. All other trademarks and registered trademarks are property of their respective owners.

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