5 virtual desktop pitfalls

Most CIOs have started considering virtual desktop infrastructure and other types of desktop virtualization, but only a minority has reached the deployment stage. (See related story, "As Windows 7 gains steam, VDI set to rise".) Virtual desktops can potentially provide more flexibility for users, make it easier to apply patches and reduce IT help desk calls, but there are still numerous problems that keep desktop pros up at night. Here are five pitfalls to watch out for.

1. Cost

There are certainly companies that have saved money by adopting desktop virtualization, but the majority won't see any ROI for at least a few years, if ever, analysts say. IT pros trying to convince management should not use cost as the main selling point, the analyst firm Forrester Research said in findings released last year.

"The nine-month ROI that vendors might advertise for their latest and greatest technologies can actually average three or four years, according to our clients that have crunched the numbers for their hosted desktop virtualization deployments," Forrester wrote. "Why? Because the upfront infrastructure and licensing costs far outweigh the upfront benefits."

VDI projects often require investment in thin clients, and improvements to storage and network infrastructure that can make it a costly project on the front end. On the flip side, virtualizing desktops can greatly extend the life of client devices, including regular desktop PCs, lowering costs in the long run.

The biggest problem preventing enterprises from virtualizing desktops is likely cost, says Burton Group analyst Chris Wolf.

"The ROI case for virtual desktops [over three to five years] is break-even at best right now," Wolf says. "Contrary to what vendors are claiming, the ROI isn't there for a large-scale, server-hosted virtual desktop deployment."

Windows licensing costs are another complicating factor in the calculation of long-term ROI. Microsoft recently lowered the price of virtual desktop operating system licenses and simplified the pricing scheme, but moving to a VDI model can still be cost-prohibitive.

2. Storage

Moving desktop images and associated data from user devices to the data center creates more stress on centralized storage systems, particularly if a project isn't planned sufficiently.

A "huge influx of data that was stored on local machines … now needs to be stored and administered centrally" because of desktop virtualization, Gartner notes in a February 2010 report.

Storage-area network (SAN) performance was the biggest problem Humberto Duarte ran into after implementing desktop virtualization at the Universite Rennes 2, a college in France where he is IT co-director.

"Our architecture for the storage was not very good. We ran into trouble [when large numbers of users accessed the network at once]," he says.

The university, which uses VMware VDI technology on Wyse thin clients, solved the problem by spreading virtual desktop data across multiple HP SANs and upgrading to faster disks.

IT manger Dan Powers of Cox Communications in Omaha, Neb., initially tested a virtual desktop deployment with a standard SAN, but found it would have raised storage costs about 8%. "It just kills our pricing model," he says. "It doesn't make sense."

Cox investigated iSCSI and found that a Dell EqualLogic system would lower costs by 14% while improving I/O performance. While Fibre Channel-based SANs were striping data across five disks, the iSCSI system was doing so across 48 disks, and using inexpensive SATA drives, he says.

"We've got more IOPS from our EqualLogic iSCSI than from our Fibre-based products," Powers says.

3. Network

If you're a typical worker who uses Microsoft Office and not much else, "200 kilobits of network bandwidth is probably enough," Wolf says.

But for workers who need video streaming and 3D graphics rendering, "those network requirements can scale to the hundreds of megabits and that's not often discussed," Wolf says. The problem isn't caused solely by desktop virtualization software makers. Most of the servers built by IBM, HP and other hardware vendors are limited in the number of slots for graphics adapters, making it difficult to scale out, Wolf says.

Network upgrades may be necessary before implementing VDI. Cox Communications upgraded its dual core switches, IDF closet equipment and 1 Gigabit uplinks before adopting VDI. Users of virtual desktops are even more reliant on the corporate network than a typical worker, because most VDI models offer little or no offline access.

"In order for us to do this, we knew up-front that our network had to be absolutely solid," Powers says. "I cannot run a VDI environment and expect the uptime to be there if I don't put the effort in."

Latency is still the enemy of desktop virtualization, Gartner says. "To date, VMware and Citrix, the industry leaders for [hosted virtual desktops], have concentrated more on 'task worker' or 'call center' environments, and thus, capabilities are limited for users that are not attached to the network continually," Gartner says. "Targeting road warriors or other mobile workers at this time is on the 'bleeding edge' because the technology is not yet tuned for offline requirements nor for managing many disparate templates or user scenarios."

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