Between today's harsh financial realities and the traction that Web 2.0 application development is gaining, it's quite possible that your next PC upgrade will involve a virtualized desktop infrastructure--a thin operating system and a browser.

As with server virtualization, total cost of ownership is not the only benefit: Virtual desktop infrastructure, or VDI, also speeds up bandwidth-intensive applications for remote workers and lets small IT staffs deploy new applications and perform reboots on demand quickly to large numbers of desktops in far-flung locales.

Still, when budgets are tight, costs are top of mind, and VDI lowers operating expenses while providing an extra dose of security--users can't install software, so a major attack vector is effectively closed down.

VDI has some shortcomings, however. End users may not be enthusiastic, and even a simple VDI environment requires a serious back-end infrastructure. The best practices suggested by VMware for its Virtual Desktop Infrastructure system, for example, advise hosting just five to eight desktops per processing core, and you'll want 1 GB of RAM per desktop.

And don't forget back-end storage: Hosted desktops require the same dedicated storage that virtualized servers do. So, if your desktop image is 10 GB after you've installed XP, Office, and all updates and applications, multiply that number by 50 when budgeting for drive space for even a small VDI implementation.

Connection brokers can mitigate some of the processing load, and disk deduplication should help reduce the amount of storage needed to host VDI virtual machines, but the resources needed are still significant. Sites with limited rack space or that are nearly maxed out on amps or cooling in the data center should be warned.

Planning ahead thoroughly has never been so important.

In this Rolling Review, we're looking to profile and test VDI packages from Citrix, Parallels, Virtual Iron, and VMware. We will also profile Virtual Access Suite, a connection broker from Provision Networks, as well as a Web-based VDI alternative from Stoneware. We'll see which of these would best meet the needs of a fictional company with 100 employees in four offices across the country. Other vendors should contact the author for consideration.