Virtualization is all over the data center and is rapidly moving onto users' desktops. As it spreads out, it's cutting hardware upgrade costs, simplifying administration from central servers, and giving users the desktops they prefer.

To continue its sweep through the enterprise, the technology needs to overcome I/O performance problems caused by running a lot of virtual machines on one server. Once the I/O issues are solved, virtualization will be more useful for both production server and end-user applications. However, in order to function well in both these areas, virtualization security must be improved as well.

Despite looming I/O and security issues, server virtualization is well established. According to Forrester Research, it has reached a "tipping point," with 23% of businesses having at least two years experience implementing the technology, and by 2009, more than half (51%) are expected to have that level of experience. Today, 24% of servers have been virtualized, says Forrester analyst Frank Gillett, and by 2009, 45% are expected to be.

NEXT UP: THE DESKTOP
There are several approaches to desktop virtualization, with no one emerging as the best. But with this technology, once you commit to an approach, it's hard to reverse course, so companies are moving cautiously. One thing that's spurring them on is the potential savings, which can match or exceed that in the data center, says Sumit Dhawan, senior manager for Citrix Systems' desktop product marketing group.

Experienced desktop virtualization vendors such as Citrix, VMware, Virtual Iron, and Hewlett-Packard offer a range of options. They can generate virtual desktops on central servers and let thousands of end users access them there or stream them to end-user machines, though this is more resource intensive. They also can generate virtualized applications and offer them as software as a service or stream just what's needed to users on demand.

	Arnett has tested the virtual desktop waters but isn't ready to let his entire company jump in Photo by Erica Berger

Sun Microsystems joins the vendor lineup, with the ability to interpret Microsoft's RDP networking protocol into user presentations on top of VMware, providing users with Solaris, Linux, and thin-client options.

But the trick to successful implementation of virtual desktops isn't which technology you pick, say two early adopters, but rather starting out with small, well-defined groups of users and developing a plan as you go.

Tony Arnett, senior systems engineer at Pentair Water Pool and Spa, has been testing virtual desktops with various groups of users for more than a year. For each target group, he builds a customized desktop, or "golden image," of a virtual machine suited to that group's needs. A golden image for accounting will have different applications and perhaps a different version of Windows than one for sales or manufacturing, though, he says, for testing purposes, he's made the images "very vanilla."

Arnett has implemented the virtual desktops on a set of three high-availability servers running VMware's ESX hypervisor and Virtual Desktop Infrastructure 3, with its tools for generating and managing VMs. Users get a Wyse V10L thin-client machine, a diskless presentation device that links to VMware's Connection Server. They self-install the thin client, connecting it to the virtual desktop using Connection Server, which manages users' access to VMs through the company's identity management system, Microsoft Active Directory.

Arnett figures if he can successfully automate the provisioning process for the first 10 users, then a hundred can easily follow.

Initially, he built a desktop for 10 IT staffers, tested it for a few weeks, and then tore it down, saving the golden image. Then he built one for 10 technical support workers, tested it, and tore it down, likewise saving the core image. He's gone through the same process with manufacturing as well as shipping and receiving, but he's not yet ready to roll out virtual desktops to the company as a whole.

Arnett has limited the test groups to 10 so he doesn't get flooded with 50 users needing information and connections at the same time. So far, the tests have been "controlled and methodical, and the desktops have worked well," he says.

Arnett is still figuring out exactly which end users and how many of them will make the switch permanently. "Quite a few departments would be perfect candidates," he says of the 1,400-employee company.