User guide

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4.1.2.1 Hypervisor Selection
Citrix XenDesktop is hypervisor agnostic, so any of the following hypervisors can be used to hosted VDI-based
desktops:
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XenServer
Citrix® XenServer® is a complete, managed server virtualization platform built on the powerful Xen®
hypervisor. Xen technology is widely acknowledged as the fastest and most secure virtualization software
in the industry. XenServer is designed for efficient management of Windows® and Linux® virtual servers
and delivers cost-effective server consolidation and business continuity. More information on Hyper-V can
be obtained at the company website.
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vSphere
VMware vSphere consists of the management infrastructure or virtual center server software and the
hypervisor software that virtualizes the hardware resources on the servers. It offers features like Distributed
resource scheduler, vMotion, HA, Storage vMotion, VMFS, and a mutlipathing storage layer. More
information on vSphere can be obtained at the company website.
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Hyper-V
Microsoft Windows Server 2008 R2 Hyper-V builds on the architecture and functions of Windows Server
2008 Hyper-V by adding multiple new features that enhance product flexibility. Hyper-V is available in a
Standard, Server Core and free Hyper-V Server 2008 R2 versions. More information on Hyper-V can be
obtained at the company website.
4.1.2.2 Provisioning Services
Hosted-VDI desktops can be deployed with or without Citrix Provisioning Sevices, but Citrix Provisioning Services
enables you to stream a single desktop image to create multiple virtual desktops on one or more servers in a data
center. This facility greatly reduces the amount of storage required compared to other methods of creating virtual
desktops. Citrix Provisioning Services desktops can be deployed as Pooled or Private:
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Private Desktop: A private desktop is a single private desktop assigned to one distinct user.
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Pooled Desktop: A pooled virtual desktop uses Citrix Provisioning Services to stream a standard desktop
image to multiple desktop instances upon boot-up.
When considering a Provisioning Services deployment, there are some design decisions that need to be made
regarding the write-cache for the virtual desktop device leveraging provisioning. The write-cache is a cache of all
data that the target device has written. If data is written to the Provisioning Server vDisk in a caching mode, the
data is not written back to the base vDisk. Instead it is written to a write-cache file in one of the locations specified
below. The following options exist for the Provisioning Services write cache:
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Cache on local HD: Cache on local HD is stored in a file on a secondary local hard drive of the device. It
gets created as an invisible file in the root folder of the local HD. The Cache file size grows as needed, but
never gets larger than the original vDisk, and frequently not larger than the free space on the original vDisk.
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Ram Cache: Cache is stored in client RAM (Memory), The Cache maximum size is fixed by a setting in
vDisk properties. All written data can be read from local RAM instead of going back to server.RAM Cache
is faster than server cache and works in a high availability environment.
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Server Cache: Server Cache is stored in a file on the server, or on a share, SAN, or other. The file size
grows as needed, but never gets larger than the original vDisk, and frequently not larger than the free
space on the original vDisk. It is slower than RAM cache because all reads/writes have to go to the server
and be read from a file. Cache gets deleted when the device reboots, in other words, on every boot the
device reverts to the base image. Changes remain only during a single boot session.