I can't put my finger on an exact date, but at some point in the past few years, virtualization changed from being marginally useful in certain scenarios for certain businesses to becoming a key piece of IT strategy for businesses of all types and sizes. The company we can and should credit for this transformation is, of course, VMware, which has been championing PC platform-based virtualization (by which I mean virtualization on the x86 and successor platforms) for more than a decade.

Recently, other companies have jumped on the virtualization bandwagon. One such company, Microsoft, got started in this market in humble fashion by buying the virtualization assets of a VMware competitor, Connectix, and rebranding its desktop-based product, Virtual PC. Since then, Microsoft has shipped various versions of Virtual Server as well. This product, which we can think of as a host-based virtualization product in that its virtual machines (VMs) sit on top of a virtualization layer that sits on top of a host OS (Windows Server in this case), was eventually made available to customers for free. But now, with its upcoming release of Windows Server Virtualization, a hypervisor-based virtualization add-on for Longhorn Server, Microsoft's been getting a lot of press. Virtualization, suddenly, is becoming mainstream.

I last wrote about Windows Server Virtualization back in November ("One Small Step for Virtualization, One Bigger Step to Come" --http://www.windowsitpro.com/Article/ArticleID/94170/94170.html ), calling it out as a major advance in Microsoft's virtualization strategy. With this technology, virtualization will run on top of Longhorn Server's so-called Server Core install, a lightweight version of the OS that essentially gives the Microsoft hypervisor a near-bare-metal installation, which should result in dramatically better performance than customers get today with host-based products such as Virtual Server.

Mindful that Microsoft is sure to steal some market share, VMware has recently begun communicating a few facts that I think are of paramount importance to anyone considering virtualization solutions in their businesses. The first may or may not be obvious: Virtualization is already a mainstream IT technology that should be embraced by companies of all sizes. The question about virtualization is no longer "if." Instead, you should be asking "where?" and "what?"

You should also be asking "which?", as in, "on which virtualization technologies should we base our business?" Microsoft, as previously reported, is working to integrate its virtualization functionality into Windows Server, and I think there's a good business case to be made there for customers looking for the most integrated and inexpensive solution. Assuming, of course, that you're purely a Windows shop.

VMware offers another solution--one that, notably, also runs on non-Windows systems. The company also pointing out, rightfully, that VMware shipped its first hypervisor-based product about six years ago and has spent the intervening years improving its virtualization technologies with new product revisions and entirely new products, many of which are concerned with VM management, provisioning, and automatic resource allotment. VMware is, in other words, still at the forefront of virtualization today and is shipping the kind of products that Microsoft has yet to create, let alone ship to the public. What VMware is selling, really, is experience, reliability, stability, and the market penetration of an unmatched virtualization ecosystem.

Regardless of which virtualization solution wins in the market place--and I do believe that market is big enough for both Microsoft and VMware to be successful--the datacenter and server rooms of the future are going to be dramatically different places as a result. VMware sees companies essentially pooling hardware resources and dynamically allocating them as required between physical and virtual environments. There will be fewer but more powerful physical servers, running the energy-efficient multicore processors that seem to have been designed almost specifically for virtualization. And with iSCSI and other storage technologies bringing down the cost of shared storage, the final piece of the puzzle is already falling into place. When thinking about technology, it's hard not to become excited about future possibilities. But in this case, I think it's also wise to become grounded in what's possible today.