IBM SmartCloud Desktop Infrastructure with Citrix XenDesktop

IBMSmartCloudDesktopInfrastructure
withCitrixXenDesktop
Reference architecture
07 February 2013
© Copyright IBM Corporation, 2013

IBM SmartCloud Desktop Infrastructure with Citrix XenDesktop
Table of contents
Introduction .................................................................................................................................1
Architectural overview................................................................................................................1
Component model.......................................................................................................................1
Citrix XenDesktop provisioning................................................................................................................4
Storage model..........................................................................................................................................6
Operational model.......................................................................................................................6
Compute servers......................................................................................................................................6
Systems management ...........................................................................................................................10
Networking.............................................................................................................................................10
Shared storage ......................................................................................................................................10
Operational model component summary...............................................................................................13
Deployment diagram..............................................................................................................................14
Resources..................................................................................................................................15
Trademarks and special notices..............................................................................................16

Introduction
This document describes the reference architecture for using Citrix XenDesktop 5.6 on VMware ESXi 5
hypervisor. It should be read in conjunction with the IBM SmartCloud Desktop Infrastructure reference
architecture available at ibm.com/partnerworld/page/stg_ast_eis_sdi_infrastructure.
The business problem, business value, and requirements are described in the IBM SmartCloud Desktop
Infrastructure reference architecture and not repeated here for brevity. This document gives an
architecture overview and component model of the Citrix XenDesktop and then describes the Deployment
model of Citrix XenDesktop using different number of users.
Architectural overview
Figure 1 shows all of the main features of the IBM SmartCloud Desktop (SDI) reference architecture with
Citrix XenDesktop. Virtual application deployment using Citrix XenApp is not included in this reference
architecture.
XenDesktop Pools
Stateless Desktops
ESXi
Hypervisor
Shared
Storage
FIREWALL
FIREWALL
Citrix
Netscaler
or 3rd party
VPN
Internet
Clients
Web
Servers
Connection
Broker
(DDC)
Internal
Clients
Active Directory, DNS SQL Database Server Provisioning Server
(PVS)
Dedicated Desktops
ESXi
Hypervisor
License
Server Machine Creation
Services
Figure 1: SDI reference architecture with Citrix XenDesktop 5.6
This reference architecture also does not address the issues of remote access and authorization, data
traffic reduction, traffic monitoring, and general issues of multi-site deployment and network management.
This document limits the discussion to the components inside the customer’s intranet.
Component model
Figure 2 is a layered view of the IBM SmartCloud Desktop (SDI) infrastructure mapped to the Citrix
XenDesktop virtualization infrastructure and using the VMware ESXi hypervisor.
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Support
ServicesSmartCloud Desktop Infrastructure - Citrix XenDesktop 5.6
Management Services
Web Server
vCenter Server
PVS or MCS
Desktop Delivery Controller
Directory
OS Licensing
DHCP
DNS
ESXi
VM
VDA
VM
VDA
VM
VDA
ESXi
Dedicated VMs Stateless VMs
Client Devices
Client
Receiver
Shared Storage
VM
Repository
Difference and
Identity Disks
User
Data Files
User
Profiles
NFS and CIFS
ManagementProtocols
SupportServiceProtocols
XenDesktop SQL Server
HTTP/HTTPS ICA
XenDesktop
Data Store
Administrator
GUIs for
Support
Services
License Server
VM
VDA
VM
VDA
VM
VDA
VM
VDA
VM
VDA
Local
SSDs
Desktop
Studio Client
Receiver
Client
Receiver
vCenter SQL Server
Figure 2: Component model for Citrix XenDesktop
The main components for Citrix XenDesktop using VMware ESXi hypervisor are described as follows. The
IBM SmartCloud Desktop Infrastructure reference architecture document available at
ibm.com/partnerworld/page/stg_ast_eis_sdi_infrastructure can be used as a guide.
 Desktop Studio Desktop Studio is the main administrator GUI for Citrix XenDesktop. It
is used to configure and manage all of the main entities including
servers, desktop pools and provisioning, policy, and licensing.
 Web Interface The Web Interface provides the user interface to the XenDesktop
environment. The Web Interface brokers user authentication,
enumerates the available desktops and, upon launch, delivers an .ica
file to the Citrix Receiver on the user‘s local device to initiate a
connection. The Independent Computing Architecture (ICA) file
contains configuration information for the Citrix receiver to
communicate with the virtual desktop. Because the Web Interface is a
critical component, redundant servers must be available to provide
fault tolerance.
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 Desktop delivery
controller
The desktop delivery controllers (DDC) are responsible for maintaining
the proper level of idle desktops to allow for instantaneous
connections, monitoring the state of online and connected desktops,
and shutting down desktops as needed.
A XenDesktop farm is a larger grouping of virtual machine servers.
The primary DDC is configured as the XenDesktop farm master
server. The master focuses on farm management while an additional
DDC acts as a dedicated XML server. The XML server is responsible
for brokering user authentication, resource enumeration, and desktop
launching. Because a failure in the XML service results in users being
unable to start their desktops, it is recommended that you configure
multiple controllers per farm.
 PVS or MCS Provisioning Services (PVS) is used to provision stateless VMs and
Machine Creation Services (MCS) is used to provision dedicated VMs.
See “Citrix XenDesktop provisioning” on page 4 for more details.
 vCenter Server vCenter Server is the managing for VMware ESXi hypervisor. Using a
single console, it provides centralized management of the virtual
machines.
Redundancy for vCenter Server is achieved through VMware HA. The
vCenter server also contains a licensing server for VMware ESXi,
 vCenter SQL Server vCenter requires a SQL database. The vCenter SQL server could be
Microsoft® Data Engine (MSDE), Oracle, or SQL Server. Because the
vCenter SQL server is a critical component, redundant servers must
be available to provide fault tolerance. Existing customer SQL
databases (including respective redundancy) can be used.
 License Server The Citrix License Server is responsible for managing the licenses for
all XenDesktop components. XenDesktop has a 30-day grace period
that allows the system to function normally for 30 days if the license
server becomes unavailable. This grace period offsets the complexity
of otherwise building redundancy into the license server.
 XenDesktop SQL Server Each Citrix XenDesktop farm requires a SQL Server database called
the data store that is used to centralize farm configuration information
and transaction logs. The data store maintains all static information
about the XenDesktop environment. Because the XenDeskop SQL
server is a critical component, redundant servers must be available to
provide fault tolerance.
 Client devices XenDesktop supports a broad set of devices, including PCs, Macs,
tablets, smartphones, and thin clients, along with all major device
operating platforms, including Apple iOS, Google Android, and Google
ChromeOS. XenDesktop enables a rich, native experience on each
device, including support for gestures and multi-touch features,
customizing the experience based on the type of device. Each client
device has a Citrix Receiver, which acts as the agent to communicate
with the virtual desktop using the ICA/HDX protocol.
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 VDA Each VM needs a Citrix Virtual Desktop Agent (VDA) to capture VM
data and send it to the Receiver in the client device. The VDA also
emulates keyboard and gestures sent from the Receiver. Note that the
VDA is different for HDX 3D Pro because it has to capture data from a
GPU rendering a 3D scene.
ICA is the Citrix display protocol for both 2D and 3D VDI.
 ESXi XenDesktop has an open architecture that supports the use of a
number of different hypervisors, such as: XenServer, Microsoft Hyper-
V, and VMware ESXi (vSphere) hypervisors. VMware ESXi is the
specific hypervisor used in this reference architecture.
 Shared storage Shared storage is used to store user profiles and user data files.
Depending on the provisioning model used, different data is stored for
VM images. Shared storage also holds the redirected vSwap files. See
Storage model on page 6 for more details.
Citrix XenDesktop provisioning
Citrix XenDesktop has two primary provisioning models:
 Provisioning Services (PVS)
 Machine Creation Services (MCS)
In summary, the ideal combination of provisioning services for XenDesktop is to use PVS for the stateless
model and MCS for the dedicated model.
Provisioning Services (PVS)
Hosted VDI desktops can be deployed with or without Citrix PVS. The advantage of using PVS is that you
can stream a single desktop image to create multiple virtual desktops on one or more servers in a data
center. Figure 3 outlines the sequence of operations run by XenDesktop to deliver a hosted VDI virtual
desktop.
vDisk
Write
Cache
SnapshotMaster
Image
Provisioning Services Server
Virtual Desktop
Request for vDisk
Streaming vDisk
Figure 3: Using PVS for a stateless model
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As soon as the virtual disk (vDisk) master image is available from the network, the virtual machine (VM) on
a target device no longer needs its local hard drive to operate; it boots directly from the network and
behaves as if it were running from a local drive on the target device. This is why PVS is recommended for
stateless virtual desktops. PVS is not generally used for dedicated virtual desktops because the write
cache is not stored on shared storage.
The size of the write cache for each VM depends on several factors, including the types of applications,
user workloads, and reboot frequency. A general estimate is 300 MB to 500 MB. Two local solid state
drives (SSDs) are configured in as RAID-0 to store the write cache. Due to the stateless nature of the
architecture, there is little added value in configuring reliable SSD drives in more redundant RAID
configurations. Redundancy is not achieved on a per host level, but achieved inherently, through the ability
of a user to connect to virtual desktops hosted on any of the remaining compute servers, in the event of an
individual server failure.
PVS is also used with Microsoft Roaming Profiles (MSRPs) so that the user’s profile information can be
separated out and reused. Profile data is available from shared storage.
It is a best practice to use snapshots for changes to the master VM images and also keep copies as a
backup.
Machine Creation Services (MCS)
Unlike PVS, MCS does not require additional servers. Instead, it uses integrated functionality built into the
hypervisor (VMware ESXi, Citrix XenServer, or Microsoft Hyper-V) and communicates through the
respective APIs. Each desktop has one difference disk and one identity disk (see Figure 4).The difference
disk is used to capture any changes made to the master image. The identity disk is used to store
information such as device name and password.
Figure 4: MCS image and difference/identity disk storage model
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There are three types of Image Assignment Models for MCS:
 Pooled-random. Desktops are assigned randomly. When they log off, the desktop is free for
another user. When rebooted, any changes made are destroyed.
 Pooled-static. Desktops are permanently assigned to a single user. When a user logs off, only
that user can use the desktop, regardless if the desktop is rebooted. During reboots, any changes
made are destroyed.
 Dedicated. Desktops are permanently assigned to a single user. When a user logs off, only that
user can use the desktop, regardless if the desktop is rebooted. During reboots, any changes
made will persist across subsequent restarts.
MCS thin provisions each desktop from a master image, using built-in technology to provide each desktop
with a unique identity. Only changes made to the desktop consume additional disk space. For this reason,
MCS dedicated desktops are used for dedicated VMs.
Storage model
This section describes the different types of shared data stored for stateless and dedicated VMs.
Dedicated VMs do not use local storage and require the following shared storage items:
 Difference disks are used to store user’s changes to the base VM image using Network File
System (NFS). The difference disks are per user and could become quite large.
 Identity disks are used store the machine name and password using NFS. Identity disks are very
small.
Both stateless and dedicated VMs have these common shared storage items:
 The master VM image and snapshots are stored using NFS
 The paging file (or vSwap) is transient data that can be redirected to NFS shared storage.
 User profiles (from MSRP) are stored using CIFS.
 User data files are stored using CIFS.
Note that Citrix XenDesktop does not use block I/O, unless thin provisioning is turned off. Not using thin
provisioning is very wasteful in regards to disk space, and is therefore not recommended.
Operational model
Two separate main operational models are considered here, to cover both stateless and dedicated image
models. In some customer environments, both stateless and dedicated image models may be required,
thus a mixed operational model is required.
In order to illustrate the operational model for different sized customer environments, four different models
are provided for supporting 600, 1500, 4500, and 10000 users. Note that the operational model for 10000
users is essentially 7 times larger than the model for 1500 users and therefore users between 1500 and
10000 can be extrapolated, by using different multiples of the 1500 user model.
Compute servers
Compute servers are servers that run the VMware ESXi hypervisor and host Citrix XenDesktop user VMs.
This reference architecture assumes a VM memory size of 1.5 GB. IBM testing has shown that 125 users
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per server with 256 GB of memory is a good baseline and has on average 75% utilization of the
processors in the server. If a server goes down, then users on that server need to be transferred to the
remaining servers. For this degraded failover case, IBM testing showed that 150 user per server will have
on average 90% utilization. It is important to keep this 25% headroom on servers to cope with possible
failover scenarios.
Other than the limit imposed by the processor power, the number of compute servers required for a given
number of users is in direct proportion to the memory size required for the VM and the number of users.
Figure 5 shows the number of users that can be supported given the VM size (on the horizontal axis) and
the amount of memory in the server given a limit of 150 users per compute server. In this reference
architecture and in most cases, IBM recommends that the compute server has 256 GB of main memory. If
the average VM size is less than 1.25 GB of memory, then 192 GB of memory is sufficient, as additional
memory would be unused. Servers requiring only 128 GB are unlikely because the cut-off point for
eliminating wasted memory is <0.75 GB per VM.
60
80
100
120
140
160
0.5 1 1.5 2 2.5 3 3.5 4
NumberofVMs
VM Size (GB)
256 192 128Memory Available on Server (GB):
Figure 5: Number of users supported by main memory and VM size
The compute servers can be either IBM x240 Flex Nodes or IBM System x3550 rack servers. The detailed
specification is as follows:
 Processor: 2 x E5-2680 8C 2.7 GHz 20 MB Cache 1600 MHz 130 W
 Memory: 256 GB as 16 x 16 GB DIMMs (2Rx4, 1.5 V PC3-12800 CL11 ECC DDR3 LP RDIMM)
 Network card: Integrated 10 GbE adapter for x240 Flex System nodes or Emulex Dual Port
10GbE SFP+ Embedded Virtual Fabric Adapter for x3350 rack servers
 USB key for VMware ESXi hypervisor
For servers with stateless VM images, the following components also need to be added:
 IBM ServeRAID M5115 SAS/SATA Controller
 2 x IBM 200GB SATA eMLC SSD (1.8 in. for x240 Flex node or 2.5 in. for x3550 rack server)
Power users require larger VMs but also need more processor power and therefore it is not usually worth
considering servers with more memory than 256 GB. If the VMs are larger than 1.5 GB, fewer users can
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be accommodated per server, thus the number of servers needs to be increased appropriately, and
memory should be sufficient again on a per-server basis. If the VMs are smaller than 1.5 GB, then
compute servers with less memory can be used because too many users would overwhelm the CPU
power of the servers.
Table 1 shows the number of compute servers needed for each user size (assuming a VM size of 1.5 GB):
VM size ≤ 1.5 GB 600 users 1500 users 4500 users 10000 users
Compute servers @125 users 5 12 36 80
Compute servers @150 users (failover) 4 10 30 70
Failover ratio 4:1 5:1 5:1 7:1
vCenter clusters (8 servers/cluster) 1 2 6 14
Table 1: Compute servers needed
Management servers
Management servers have the same hardware specification as compute servers so they could be used
interchangeably in a worst-case scenario. The management servers also use ESXi as the hypervisor but
have management VMs instead of user VMs.
Table 2 summarizes the VM requirements and performance characteristics of each management service.
Management
service VM
Virtual
processors
Memory Storage Windows
OS
HA
needed
Performance
characteristic
vCenter server 4 4 GB 15 GB 2008 R2 No Up to 2000 VMs
vCenter SQL
server
4 4 GB 15 GB 2008 R2 Yes Double the virtual
processors and
memory for more
than 2500 users
DDC 4 4 GB 15 GB 2008 R2 Yes 5000 user
connections
Web server 4 4 GB 15 GB 2008 R2 Yes 30,000 connections
per hour
Licensing server 2 4 GB 15 GB 2008 R2 No 170 licenses per
second
XenDesktop SQL
server
2 4 GB 15 GB 2008 R2 Yes Double the virtual
processor and
memory for more
than 2500 users
PVS servers 4 32 GB 40 GB 2008 R2 Yes Up to 1000 VMs,
memory should be
a minimum of 2 GB
plus 1.5 GB per
image served
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Table 2: Characteristics of management services
Table 3 lists the number of management VMs for each size of users following the high-availability and
performance characteristics listed. Note that the number of vCenter servers is half of the number of
vCenter clusters shown in Table 1. This is because each vCenter server can handle two clusters of up to
1000 VMs, and each cluster exists on two vCenter servers.
Management service VM 600 users 1500 users 4500 users 10000 users
vCenter servers 1 1 3 7
vCenter SQL servers 2 (1+1) 2 (1+1) 2 (1+1) 2 (1+1)
Desktop Delivery Controllers
 Includes Citrix Licensing server
 Includes Web Server
2 (1+1)
Y
Y
2 (1+1)
N
N
2 (1+1)
N
N
2(3+1)
N
N
Web servers N/A 2 (1+1) 2 (1+1) 2 (1+1)
Licensing servers N/A 1 1 1
XenDesktop SQL servers 2 (1+1) 2 (1+1) 2 (1+1) 2 (1+1)
PVS servers for stateless case only 2 (1+1) 4 (2+2) 8 (6+2) 14 (10+4)
Table 3: Management VMs needed
Note that it is assumed that common services such as Microsoft Active Directory, DHCP, DNS, and
Microsoft licensing servers already exist in the customer environment.
Based on the number and type of VMs, Table 4 lists the recommended number of management servers. In
all cases, there is redundancy in both the management servers and the management VMs.
Management servers 600 users 1500 users 4500 users 10000 users
Stateless VM model 2 2 4 7
Dedicated VM model 2 2 2 4
Table 4: Management servers needed
As documented earlier, each management VM requires a certain amount of virtual processors, memory
and disk. Note that there is plenty of capacity in the management servers for all of these VMs. Table 5 has
an example mapping of the management VMs to the 4 physical management servers for 4500 users.
Management service for 4500
stateless users
Management
server 1
Management
server 2
Management
server 3
Management
server 4
vCenter servers (3) 1 1 1
vCenter database (2) 1 1
XenDesktop database (2) 1 1
DDC (2) 1 1
Web server (2) 1 1
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License server (1) 1
PVS servers for stateless case only (8) 2 2 2 2
Table 5: Management server VM mapping (4500 users)
Systems management
Assuming the use of IBM Flex System compute servers, it is recommended to have one or more IBM Flex
System Manager nodes, especially in case of the larger configurations, to provide additional systems
management capability.
Networking
As described in the IBM SmartCloud Infrastructure reference architecture available at
ibm.com/partnerworld/page/stg_ast_eis_sdi_infrastructure there are 3 virtual LANs (VLANs) that each
share part of the bandwidth in a 10 GbE network. All of the compute servers, management servers, and
shared storage are connected to the 10 GbE network using a 10 GbE switch. The IBM RackSwitch
G8124E and G8264R switches are recommended as they support VLANs using IBM Virtual Fabric. Note
that although the IBM PureFlex™ chassis supports internal 10 GbE switches, these are not used because
a separate switch is needed for the external shared storage. The IBM Flex System Fabric EN4091 Pass-
thru Module is used to pass the 10 GbE connections to the external switch.
For fewer than 4500 users the IBM G8124E 24-port switch can be used. Above 4500 users, multiple IBM
G8264R 48-port switches should be used instead as these switches provide more ports. For redundancy
an additional or spare switch should be available. Table 6 summarizes the number of 10 GbE switches for
each user size:
10 GbE network switch 600 users 1500 users 4500 users 10000 users
G8124E – 24-port switch 2 (1+1) 2 (1+1) 3 (2+1) 0
G8264R – 48-port switch 0 0 0 3 (2+1)
Table 6: 10 GbE network switches needed
Separate 1 GbE switches are used for the IT administration network. Again, it is recommended that a
spare switch be available in case of failure. Table 7 summarizes the number of 1 GbE switches for each
user size:
1 GbE network switch 600 users 1500 users 4500 users 10000 users
G8052 – 48 port switch 2 (1+1) 2 (1+1) 2 (1+1) 3 (2+1)
Table 7: 1 GbE network switches needed
For smaller configurations and Flex-based systems, consider consolidating the 1GbE network into the
10GbE switch using SFP RJ45 transceivers
Shared storage
VDI workloads such as virtual desktop provisioning, VM loading across the network, and access to user
profiles and data files place huge demands on network shared storage. This reference architecture first
describes the performance requirements of both stateless and dedicated virtual desktops and then shows
the storage configuration that meets those requirements.
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Experimentation with VDI infrastructures shows that the input/output operation (IOP) performance takes
precedence over storage capacity. This means that more of the slower speed drives are needed to get the
required performance than higher speed drives. Even with the fastest drives available today (15k RPM),
there is still can be an excess capacity in the storage system.
The large rate of IOPs and therefore large number of drives needed for dedicated virtual desktops can be
ameliorated to some extent by caching read data in flash memory (flash cache feature of some N series
controllers). However there is a limit to how much flash memory is useful because of the relatively low
percentage of read operations.
In terms of the IBM N series range of storage systems, the largest 15k RPM SAS drive is 600 GB. These
disks require a larger expansion cabinet with 24 disks in a 4U enclosure. The same number of slower-
speed 10K SAS drives in a small form factor (SFF) 2.5 in. can be put in a 2U enclosure. In this case
superior performance wins over the cost of rack density and the storage configurations all use 600 GB 15k
RPM SAS drives.
The storage configurations are based on the peak performance requirement, which usually occurs during
a so-called “logon storm”. This is when all workers at a company arrive at the same time in the morning
and try to start their virtual desktops, all at the same time. The storage configurations also have
conservative assumptions about the VM size, changes to the VM, and user data sizes to ensure that the
configurations can cope with the most demanding user scenarios.
As mentioned above the storage configurations tend to have more storage that is strictly required in order
to meet the performance objectives for IOPs. In our experience this “extra” storage is more than sufficient
for the other types of data needed for VDI such as SQL databases and transaction logs.
Note that the storage configurations do not include facilities for data replication, data compression, or data
deduplication. These are all value-added features that may or may not be required. These features may
also have an effect on the storage configuration. The storage configurations, where possible, do include
flash memory as a means to cache frequently used data.
Stateless virtual desktops
Stateless virtual desktops using Citrix XenDesktop are provisioned from shared storage using PVS. The
PVS write cache is maintained on a local SSD. Table 8 summarizes the peak IOPs and disk space
requirements for stateless virtual desktops on a per-user basis.
Citrix stateless virtual desktops Protocol Size IOPs Write %
User data files CIFS/NFS 5 GB 1 75%
User profile (through MSRP) CIFS 100 MB 0.8 75%
Table 8: Stateless shared storage performance requirements
Table 9 summarizes the storage configuration needed for each user size. In this case, the flash cache
does not help at all, so a lower end controller with failover is used. It is also assumed that 100% of the
users at peak load times require concurrent access to user data files and profiles.
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Stateless storage 600 users 1500 users 4500 users 10000 users
Controller and model number N3220 A22 N3220 A22 N3220 A22 N3220 A22
10 GbE mezzanine cards 2 2 2 2
Flash cache N/A N/A N/A N/A
600 GB 15K rpm drives 12 20 70 164
Spare drives 2 2 2 4
EXN3000 expansion unit 1 1 3 7
Table 9: Stateless shared storage configuration
Dedicated virtual desktops
Table 10 summarizes the peak IOPs and disk space requirements for dedicated virtual desktops on a per-
user basis. The last two rows are the same as used for stateless desktops.
Citrix dedicated virtual desktops Protocol Size IOPs Write %
Master image NFS 30 GB
Difference disks
User “AppData” folder
NFS 10 GB
18 85%
User files CIFS/NFS 5 GB 1 75%
User profile (through MSRP) CIFS 100 MB 0.8 75%
Table 10: Dedicated shared storage performance requirements
Table 11 summarizes the storage configuration needed for each user size. A mid-range controller with 512
MB of flash cache is used for fewer than 2000 users as it supports up to only 600 drives. A high-end
controller is used for more than 2000 users because it has a larger flash cache capability, more 10 GbE
ports, and can support up to 1440 drives. It is also assumed that 100% of the users at peak load times
require concurrent access to user data files and profiles.
Dedicated storage 600 users 1500 users 4500 users 10000 users
Controller and model number N6240 E21 N6240 E21 N7950T E22 N7950T E22
10 GbE cards 2 2 2 2
Flash cache 512 MB 512 MB 1 GB 1 GB
600 GB 15K rpm drives 42 100 296 630
Spare drives 6 8 24 42
EXN3000 expansion units 2 6 16 28
Table 11: Dedicated shared storage configuration
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Operational model component summary
Table 12 summarizes the items needed for stateless virtual desktops for each user size:
Stateless virtual desktop 600 users 1500 users 4500 users 10000 users
Compute servers 5 12 36 80
Management servers 2 2 4 7
10 GbE network switches 2 x G8124E 2 x G8124E 3 x G8124E 3 x G8264R
1 GbE network switches 2 x G8052 2 x G8052 2 x G8052 3 x G8052
PureFlex Flex System Manager nodes
(optional, only for Flex)
1 1 2 2
Flex chassis with EN4091 pass-thru
module (only for Flex)
1 1 3 7
Storage servers N3220 A22 N3220 A22 N3220 A22 N3220 A22
Storage extensions EXN3000 x 1 EXN3000 x 1 EXN3000 x 3 EXN3000 x 7
Total height (Flex System servers) 20U 20U 49U 109U
Total height (x3550 rack servers) 17U 24U 59U 127U
Number of racks 1 1 2 3 or 4
Table 12: Operational model summary for stateless virtual desktops
Table 13 summarizes the items needed for dedicated virtual desktops for each user size:
Dedicated virtual desktop 600 users 1500 users 4500 users 10000 users
Compute servers 5 12 36 80
Management servers 2 2 4 8
10 GbE network switches 2 x G8124E 2 x G8124E 3 x G8124E 3 x G8264R
1 GbE network switches 2 x G8052 2 x G8052 2 x G8052 3 x G8052
PureFlex Flex System Manager nodes
(optional, only for Flex)
1 1 2 2
Flex chassis with EN4091 pass-thru
module (only for Flex)
1 1 3 7
Storage servers N6240 E21 N6240 E21 N7950T E22 N7950T E22
Storage extensions EXN3000 x 2 EXN3000 x 6 EXN3000 x 16 EXN3000 x 28
Total height (Flex System servers) 28U 44U 111U 203U
Total height (x3550 rack servers) 25U 48U 121U 221U
Number of racks 1 1 3 6
Table 13: Operational model summary for dedicated virtual desktops
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Deployment diagram
Figure 6 shows the deployment diagram for an IBM Flex System-based system that supports 4500
stateless users. The first rack contains the compute and management servers and the second rack
contains the storage servers and disks.
EN4091Pass-thruEN4091Pass-thruEN4091Pass-thru
M1
C11 C12
C9 C10
C7 C8
C5 C6
C3 C4
C1 C2
1 GbE Switch
1 GbE Switch
10 GbE Switch
10 GbE Switch
FSM M2
C23 C24
C21 C22
C19 C20
C17 C18
C15 C16
C13 C14
FSM M3
C35 C36
C33 C34
C31 C32
C29 C30
C27 C28
C25 C26
M4
Rack 2
10 GbE Switch
DS4243 Extension
(24 x 600GB 15k RPM)
DS4243 Extension
(24 x 600GB 15k RPM)
M1 VMs
vCenter Server
vCenter SQL Server
DDC
PVS Servers (2)
M4 VMs
Desktop SQL Server
DDC
Web Server
PVS Servers (2)
M2 VMs
vCenter Server
vCenter SQL Server
License Server
PVS Servers (2)
M3 VMs
vCenter Server
Desktop SQL Server
Web Server
PVS Servers (2)
Cxx
Each compute
server has
125 user VMs
Rack 1
FlexChassis1FlexChassis3FlexChassis2
IBM N3220 A22
DS4243 Extension
(24 x 600GB 15k RPM)
Figure 6: Deployment diagram for 4500 stateless users
14

Resources
 IBM SmartCloud Desktop Infrastructure reference architecture
ibm.com/partnerworld/page/stg_ast_eis_sdi_infrastructure
 Citrix XenDesktop
citrix.com/products/xendesktop
 VMware vSphere
vmware.com/products/datacenter-virtualization/vsphere
15

16
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