Fluid desktops

Spurred by the business benefits gained from server virtualization, enterprises now are embracing desktop virtualization for many of the same reasons: flexibility, lower costs and ease of management.

The latter has been huge for the University of Maryland in College Park, says Jim Maloney, network applications manager at the school, which has been using desktop virtualization since November 2007. The university hosts 50 -- soon to be 250 -- virtual PC images on two VMware ESX servers running the Sun Ray Server Software and Sun's virtual desktop software. Users access the images from Sun Ray terminals. "Overall, we've saved 30 hours a week in management time -- practically one full-time employee," he says.

Others look to desktop virtualization as a hedge against the cost of future PC upgrades. "Compared with traditional desktops, virtualization is a no-brainer," says Kunal Patel, IT manager at Nina Plastics, a packaging manufacturer in Orlando. Nina hosts 50 virtual PC images on two ESX servers using Pano Logic's Virtual Desktop Solution software. Users access the hosted images from a specialized hardware-only device into which they plug their mice, keyboards, displays and network connections.

"We were spending between $700 and $1,000 per desktop, whereas the Pano device costs just $300. And an actual PC eventually becomes obsolete and has to be replaced. With the Pano, if we want to upgrade the entire company's desktops, we just upgrade the few servers we have and we allot more memory or faster speeds to the images. It's a concrete dollar savings," Patel says.

Plus, users get unprecedented flexibility: They can access their desktops from virtually any device residing anywhere, as long as they have good network connections. Instead of sharing centrally hosted applications, they access their full desktop images complete with familiar applications and customized wallpaper -- the final fulfillment of the thin-client ideal.

One, two, three approaches

Desktop virtualization requires a hypervisor, such as VMware ESX, Citrix Systems XenServer or Microsoft Hyper-V, running on a data-center server to host the desktop images. Vendors differentiate themselves by the overlying desktop virtualization-management software that brokers the connection between the virtual PC image and the actual client, be that a Macintosh, Linux or Windows PC; thin client; RDP

Web browser; or specialized device such as the Pano. While many vendors rely on Microsoft's Remote Data Protocol (RDP) to handle the server-client communications (think Microsoft, VMware), others use proprietary protocols to apply compression and other optimization techniques. For example, Citrix uses its well-known Independent Computing Architecture (ICA) communications protocol, while Qumranet has a rendering protocol, called Simple Protocol for Independent Computing Environments, aimed at supporting multimedia applications.

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Three caveats for desktop virtualization

Vendors are addressing different use cases and pain points. The most well-known approach, called VDI (after VMware's pioneering Virtual Desktop Infrastructure), lets IT host a virtual desktop image on a data center server. The virtual desktop, which users access via an always-on network connection, remains secure, backed up and easy to manage.

VDI also offers good disaster recovery, because backing up a single server to a disaster-recovery site is easier than recovering multiple distributed desktops. "If you were in the Midwest flood zone and some office received damage and couldn't open, those employees could work remotely from home or from somewhere else in the country," says Mitchell Ashley, CEO of Converging Network and a Network World Microsoft Subnet blogger.

VDI also handles day-to-day disasters more easily than a physical desktop infrastructure can. When PCs fail, users lose work, time and, usually, data. A virtual PC is not tied to hardware, however, so fixing what's gone awry usually means just restarting the session. Data should be current because it sits on a server.

Likewise, virtual PC users shouldn't be affected when a host server fails. At Nina Plastics, for example, Patel uses two servers for failover protection. He describes how effective that approach has been for business users: "One day, something happened with one of the servers and it stopped running. I only noticed because I was walking through the data center and I saw the light was off. I went around the office and asked if anybody noticed anything slow or wrong, and nobody mentioned anything."

That situation was a far cry from the past, when Patel continually chased down desktop problems. "In the past, a server failure would have been a nightmare. I would have had 1,000 calls. But with this setup . . . everyone continued to do business."

VDI also is easier to secure than a physical desktop infrastructure because security updates and patches can be made to the image template once, and users get the changes the next time they access their desktops. In addition, user access to USB, thumb, CD and DVD drives and other peripherals can be restricted centrally and, because VDI's images are full desktops, they include such corporate security features as VPN support.

On the downside, a centrally hosted VDI requires an always-on network connection. While this kind of connection is becoming more ubiquitous in these days of wireless and broadband, it still is not a given. "You can't use VDI on a plane or in a subway tunnel," Converging Network's Ashley notes.

In addition, many graphics- or processor-intensive desktop applications don't work as well via a VDI as they do over a physical infrastructure. Bottlenecks occur when all the desktops share the host server's processor and memory. The performance of such interactive applications as video also tends to suffer with VDI, primarily because all execution happens on the server and is presented to the user via a remote presentation protocol -- RDP, for example -- that's not optimized for streaming.