Once you've figured out the appropriate use cases, INX's Kaplan recommends creating a project definition document that clearly states the business reasons behind the project, as well as the benefits and expected ROI. "When you hit the inevitable hurdles -- like when the assistant to the vice president breaks down because he can't print and wants to get rid of this VDI stuff -- you'll have this touchstone you can go back to."
Hosting virtual desktops is about separating the physical personal computing device from the Windows operating system and applications, which normally run on top of it, and moving it into the data center, where it can be more easily managed. Vendors offer several variations on this theme.
Understand the technology options
The most popular technology today for desktop virtualization is VDI. This is exemplified by VMware View, in which instances of Windows XP or Windows 7 run within virtual machines that are separated from the underlying physical server host. This separation happens by way of a layer of software, such as the VMware vSphere Hypervisor. That software lets each virtual PC think it has exclusive access to the hardware while serving as the traffic cop for all requests to the shared hardware underneath it.
Rent-A-Center: Virtual desktops trump laptops
KC Condit, senior director of information security and support services at Rent-a-Center, faced a challenge. Some managers of the rent-to-own retail store chain needed access to corporate applications, both from the six to eight stores they visit each week and from home.
In addition, the 13,000 aging Windows XP thin clients in the stores are slow -- and users don't always like the look and feel of the thin clients. Managers can use these clients to connect to their applications by way of the Web-based user interface delivered by Citrix's XenApp.
The thin clients, which need a local browser to function, had already been updated to run Internet Explorer 7. But the limited compact flash memory in each machine couldn't keep up with temp file, swap space and other storage needs, while Web-centric programs like Flash bogged down the processors, Condit says.
Rather than issuing laptops to all 425 managers, Condit launched a XenDesktop pilot to improve performance from the stores' aging thin clients, since no local browser is needed, and to allow managers to securely access their virtual desktops and hosted data from any personal computing device, either at home or at work.
Jai Chanani, senior director of technical services and architecture, worked on the networking and data center infrastructure for the pilot. The project is, he says, a cost-avoidance play. The goal is to extend the life of the thin clients by presenting applications in a hosted Windows 7 environment, and avoid the need to invest in laptops and related endpoint security to protect corporate data.
There were some infrastructure issues to address. Rent-A-Center ended up switching to a different SAN and a new caching algorithm for its desktop virtualization back end. Bandwidth needs have also factored in. "It's not just the amount of bandwidth that desktop virtualization uses but when you are using it," Chanani says. The analysis is still in the early stages, but so far Rent-A-Center has needed to upgrade network links at 10% of its locations.
What users are allowed to do also needs to be controlled. For example, users can print at work but not from home, no data resides locally, and data cannot be copied to the user's local device or to a USB disk.
The project is on track to begin production deployments in the second quarter of this year.
-- Robert L. Mitchell
Of course, you can define desktop virtualization more broadly -- as a way to remove the Windows desktop environment from the physical PC and host it in the data center. This idea has actually been around since Microsoft introduced Terminal Services (now Remote Desktop Services) with Windows NT 4.0 back in 1996.
This software served up hosted Windows applications within terminal sessions, with Windows Server functioning as the underlying multiuser operating system. Citrix has extended that approach to include the presentation of a simulated Windows desktop operating system environment using RDS/Windows Server.
In both cases, the connection methodology is similar: A physical client (either a thin client or personal computer running special client software) exchanges keystroke, mouse and display information with a simulated Windows desktop running in a terminal session, or a Windows virtual machine residing on a back-end host.
The technology has improved since those early days of server-based computing. Today the performance is faster than ever, the user's virtual desktop can include whatever level of personalization that company policies allow, and in the RDS model, users can work within a complete virtual desktop environment rather than pick from a slim menu of virtualized applications.