What began as an effort to run multiple operating systems on a workstation has evolved into the core technology that will define IT for the foreseeable future. Not only will virtualization never go away, it's going to completely take over every level of IT infrastructure. But if that's the goal, where are we on the timeline? Further along than you might otherwise think, depending on the virtualization platform you're running.
The world of x86 server virtualization breaks down fairly cleanly along vendor lines: those that are running VMware and those that aren't. If you're running VMware ESX 3.5 or vSphere, you're well ahead of the general curve. You enjoy critical functions like vMotion, Storage vMotion, DRS (Dynamic Resource Scheduling), HA (High Availability), physical page sharing to reduce overall RAM requirements, and a plethora of other enterprise features that define VMware as far and away the leading virtualization platform available today.
[ For a thorough evaluation of VMware's latest offering, read Paul Venezia's detailed review: "VMware vSphere 4: The once and future virtualization king." ]
If you're not running VMware, you're running Microsoft's Hyper-V, Citrix XenServer, or one of a handful of smaller hypervisors. You may be running production systems on these tools, but they each lack critical components present in VMware's offerings. Citrix XenServer is further along and more mature than Hyper-V, but it still cannot compare directly with vSphere or even its predecessor, VI3. In fact, both companies essentially refuse to compare their products directly, opting to compare their offerings with VMware's free ESXi embedded hypervisor. These are disingenuous comparisons, but it's all they have. Microsoft is making strides with the pending release of Hyper-V Server 2008 R2, which will support Live Migration and a smattering of other features, but that still brings them up to par with where VMware was four years ago.
This isn't necessarily a good thing for IT in general -- stiff competition generally leads to better, cheaper solutions all around -- and Microsoft and Citrix are certainly working hard to catch up. But they can't avoid the hard reality that they're several years behind on the development curve. They'll get there eventually, but how far ahead will VMware be at that point? Let's hope, at least, that Microsoft and Citrix will advance far enough to force VMware to lower prices.