The VDI Deployment Mine Field


In September, 2010, more than 80 percent of enterprises were said to have a virtualization program or project in place. That's according to a Gartner report,
which also declared that only 25 percent server workloads would be running in virtual machines by the end of that year. This leaves an enormous amount of virtualized computing bandwidth -- 80 to 90 percent, the researcher estimated -- on the table.

With that kind of server infrastructure in place, there's little to prevent the virtual desktop infrastructure from taking hold. Or is there?

Gartner in the same release said that such virtual desktop infrastructure (VDI) user environments, which it calls hosted virtual desktops (HVDs), represent tremendous potential for power savings, ease of centralized administration and speed and flexibility of deployment.

"HVDs are poised to undergo explosive growth, and enterprises are anticipating the flexibility and other benefits that these devices will bring," said Philip Dawson, research vice president at Gartner. "HVDs provide end-user flexibility, efficiency, energy savings and other benefits, enabling administrators to manage desktops from a centralized location and end users to access their desktops from machines in any location."

There's no single way to define VDI (or HVD), but the technology has been traditionally defined as a transfer of the thick desktop client running on a PC that's located near the user, to the execution of the users' local environment in a virtual machine hosted on a network server, where it can be accessed from any number of thick, thin, or "zero" client systems and utilities.

Once past the major migration hurdles, VDI benefits IT by moving most of the desktop OS management chores away from far-flung desktops and into the data center, where maintenance activities can be centralized and made more efficient, and where protection processes can be institutionalized. Users can access their apps and data from anywhere, as long as they're connected to the company network.

Next: The VDI DownsidesBut VDI also has some serious downsides.

Apps and data must be transferred from each user's local machine to the virtualization server's storage environment. Virtualization severs each require one or more hypervisor licenses (usually priced per-processor) plus lots of server horsepower and storage capacity.

Then there are the increases in power, cooling and utility bills required to keep a more active data center humming.

"[E]nterprises need to understand the strain this technology can place on their data center infrastructures and operations, especially when thousands of employees use this platform type," said Dawson.

From the end-user's perspective, virtualized desktops often run (or appear to run) more slowly than their native counterparts, particularly for graphics-intensive applications. They also present new challenges for accessing local peripherals such as printers, scanners and drives.

Then there's the issue of client licensing. Windows licenses transfer directly to the virtualization server without issue. But as of July, 2010, access devices that are not running Windows or don't otherwise come under a Microsoft Software Assurance plan could be subject to a $100 per-device, per-year Virtual Desktop Access (VDA) licensing fee. Yup, that's $100 per device, per year.

For example, an executive can access his VDI desktop using a laptop running Windows, but if he wants to bring it up on a smart phone, someone needs to buy a VDA. Once licensed, however, the VDA's roaming provision permits that user to access as many as four VDI images (virtual machines) from "any device outside the corporate environment," according to a Microsoft FAQ (PDF) on the subject. Such devices might include public kiosks, home computers and the like.

Gartner characterizes licensing as a "major stumbling block" to widespread adoption of virtualization and VDI, and advises that companies plan to spend more time on contract negotiations and understand completely the changes in vendor pricing and licensing agreements or face significant cost increases.