In the first
part of this series
, we reviewed some of the benefits and drawbacks to
desktop virtualization. On the positive side of the ledger, users can now
access a corporate-approved image or suite of applications, independent of
hardware, facilitating BYOD or mobile initiatives while maintaining IT control.

With all the pros of moving desktops into the data center come some cons,
mainly pushing what was once a distributed computing model into a central
location, increasing demands on the data center in terms of processing, power,
and associated maintenance. With benefits and drawbacks in mind, let’s look at the
pragmatic side of a virtual desktop infrastructure (VDI).

Three takes on the
virtual desktop

One of the main points of confusion about virtual desktop
technology is how it differs from traditional “server hosted” desktops
pioneered by companies like Citrix and Microsoft, whereby a user creates a
terminal session with a server, where he or she is presented with their own
“hosted” desktop environment.

Terminal-style “virtualization” is more akin to time sharing
from the mainframe era; a server presents multiple end-user sessions, executed
and managed by the server OS. With desktop virtualization, the server
partitions each desktop into a virtual machine, allowing the virtual desktop to
be moved between servers and storage, allocated fungible resources, or provisioned
and modified on the fly.

Virtual desktops can be further divided into “shared
image” desktops that essentially use a single, standardized desktop image to
serve all users, or “personal image” desktops, which provide the user with
their own VM that can be modified and customized just like a standard physical

Each vendor has its own take on these two broad categories, with their
own nomenclature, but the tradeoff is essentially allowing end-user
customization at the cost of increased maintenance, versus maintaining only a
single image for several users.

From an end user perspective, the three experiences are
largely the same. The user opens a client or viewer application and connects to
a desktop that is hosted elsewhere. Depending on the configuration, the user
may or may not be able to store files locally on that desktop, or modify the
configuration and installed applications.

Virtual players

The big three vendors in desktop virtualization are the same
as the data center, with Citrix, Microsoft, and VMware each presenting an
offering specifically targeted at desktop and application virtualization.

What’s interesting about desktop virtualization is that the management and
provisioning layer can be separated from the hypervisor that actually executes
virtual desktop images, allowing one vendor to serve as virtual desktop
“controller,” while the actual virtual desktops run in the same VMware or
Hyper-V hypervisor already deployed in your data center.

Citrix is the leader in desktop and application
virtualization due to its long presence in terminal-based shared desktops. I
also find Citrix’s XenDesktop to be more mature on the mobile front, offering
application and desktop virtualization to Android and iOS devices.

In addition
to the IT management benefits of VDI, Citrix allows you to quickly move your
existing applications to mobile through application virtualization. This also
expands your BYOD options, allowing your corporate Windows desktop image to run
on anything from Android to OS X.

Microsoft’s main advantage in the VDI space is that they own
the desktop OS and many common management tools. If you’re a Microsoft shop, you
may already own most of the components of their VDI suite, as the functionality
and hypervisor are native to Server 2012, management is embedded in recent
versions of Systems Center, and Windows 7 and 8 include support for Microsoft’s
desktop and application virtualization technologies.

VMware hopes to leverage its obvious strength in the data
center with its VDI offering, and also implements the proprietary PCoIP
(Pixel-Compression over IP) protocol, which provides accelerated video
rendering in the data center and video compression to the client, making for a
faster user experience on compatible clients.

While its VDI product, VMware
Horizon, is less mature than Citrix, other vendors will happily interoperate
with a VMware hypervisor infrastructure, allowing for what amounts to a best of
breed solution.

With better VDI management, increased interest in BYOD, and
an eye toward bringing the benefits of data center virtualization to the
desktop, interest in VDI technologies has grown. The technology has matured,
and the three major virtualization players have capable offerings. While VDI is
not right for all scenarios, it’s a relatively low-cost way to enable popular
policies like BYOD while reducing the cost of provisioning and deploying
corporate desktops, and may be worth revisiting as you plan your coming IT