Hosting virtual desktops: Tips for a successful outcome

Be prepared for a long road; the technology requires a significant buildup of servers and other infrastructure, among other things

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Hosted desktop virtualization

You virtualize the entire Windows desktop environment, including applications, and host them in the data center. The user then interacts remotely with the hosted virtual desktop by exchanging keystroke, mouse and video screen updates with it.

Vendors offer two approaches based on the VDI model. Under the first option, the persistent VDI design gives every user his own virtual desktop that runs within a virtual machine on a back-end server. Each user gets his own virtual desktop that spins up from a unique, dedicated virtual machine image file containing a full install of Windows. The user owns the image, and any changes that he makes to it will be saved.

The second option presents a "nonpersistent" virtual desktop, which gets spun up on demand from a common "golden" image file and serves multiple users. When a user logs out, any changes made to the virtual desktop disappear.

Citrix presents a third option: Its "hosted shared virtual desktop" follows its XenApp/Presentation Server (server-based computing) model by offering up a simulated Windows desktop in an RDP session on Windows Server.

In cases where organizations were already using XenApp for application delivery, some IT departments have decided it would be more cost-effective to roll out XenApp as a platform for hosted shared virtual desktops rather than build a new infrastructure for VDI, says INX's Kaplan. Technically, however, he doesn't consider it to be a virtual desktop technology, since users are really running a shared Windows Server operating system, not a native Windows XP or 7 desktop operating system hosted within a virtual machine.

"While it is possible to do almost anything with XenApp that one can do with VDI, it can become very complex and burdensome. That is why it never took off as a mainstream desktop replacement solution despite the overwhelmingly compelling economics," Kaplan says. "At the root of the problem, you have Windows Server being used in a way it was never designed for."

Most of the Citrix virtual desktop deployments he's seen to date have used Citrix's XenDesktop to host nonpersistent VDI desktops, he says.

Going with the approach of nonpersistent virtual desktops saves on back-end management and infrastructure costs, since the approach uses a few golden image files rather than one for each user, and that takes up less networked storage space.

When users log out, their virtual desktops can be shut down. But it's more typical to keep the virtual desktops in a suspended state so that users can get up and running more quickly when they log back in. In fact, for nonpersistent virtual desktops, administrators may keep a pool of virtual machine sessions running or in a suspended state all of the time so that new users can get up and running quickly after logging in.

Before rolling out VDI, slow boot-up times on older PCs were one of the biggest user complaints, says Kevin Summers, CIO at Whirlpool. Now, early users of VDI are finding that they're up and running more quickly. "Employees aren't as frustrated," he says. [See sidebar.]

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