Desktop virtualization harks back to the good old mainframe days of centralized computing while upholding the fine desktop tradition of user empowerment. Each user retains his or her own instance of desktop operating system and applications, but that stack runs in a virtual machine on a server -- which users can access through a low-cost thin client similar to an old-fashioned terminal.
The argument in favor of desktop virtualization is powerful: What burns through more hands-on resources or incurs more risk than desktop computers? Even with remote desktop management, admins must invade cubicles and shoo away employees when it's time to upgrade or troubleshoot. And each desktop or laptop provides a fat target for hackers and an opportunity to steal data.
[ Wondering which server-based computing solution is right for you? Read Paul Venezia's Thin Client Computing Deep Dive and get the whole story. ]
But if you run desktops as virtual machines on a server, you can manage and secure all those desktop user environments in one central location. Patches and other security measures, along with hardware or software upgrades, demand much less overhead. And the risk that users will make mischief or mistakes that breach security drops dramatically.
The argument against desktop virtualization is almost as strong. Overhead costs conserved through central management get cancelled out by the need for powerful servers, virtualization software licenses, and additional network bandwidth. Plus, the cost of client hardware and Microsoft software licenses stays roughly the same, while the user experience -- at least today -- seldom lives up to user expectations. And then the kicker: How are users supposed to compute when they're disconnected from the network?
Decisions about whether or in what form to adopt desktop virtualization become a whole lot easier when you understand the basic variants and technologies. Here's what you need to know:
1. Desktop virtualization really is virtualization
Just like server virtualization, desktop virtualization relies on a thin layer of software known as a hypervisor, which runs on bare-metal server hardware and provides a platform on which administrators deploy and manage virtual machines. With desktop virtualization, each user gets a virtual machine that contains a separate instance of the desktop operating system (almost always Windows) and whatever applications have been installed. To the desktop OS, the applications, and the user, the VM does a pretty good job of impersonating a real desktop machine.
2. Traditional thin client solutions are not desktop virtualization
By far the most popular form of server-based, thin client computing relies on Microsoft Terminal Services (recently renamed Remote Desktop Services), which lets multiple users share the same instance of Windows. Terminal Services is often paired with Citrix XenApp (formerly known as Presentation Server and, before that, MetaFrame), which adds management features and improves performance -- no hypervisors or VMs here. The main drawbacks: Some applications run poorly or not at all in this shared environment, and individuals can't customize their user experience the way they can with virtual machines or real desktops. Nonetheless, people often refer to traditional thin client solutions as desktop virtualization because the basic goal is the same: to consolidate desktop computing at the server.