How fast is the shift to server virtualization happening? According to Gartner, 18 per cent of server workloads this year run on virtualized servers; that share will grow to 28 per cent next year and reach almost half by 2012.

Large enterprises have driven server virtualization over the last four years or so, and VMware holds an 89 per cent market share against a handful of competitors that include Microsoft, Citrix, Red Hat and others. There are about 5.8 million virtual machines (VM) believed to be in use today, said Gartner analyst Thomas Bittman, speaking on the topic Monday at Gartner's Symposium ITExpo 2009 attended by thousands of high-tech managers from around the world.

But growth is anticipated among the small-to-midsize businesses (SMB), and it's in this segment that Microsoft has a good chance to build a customer base. By 2012, VMware's share is expected to shrink to 65 per cent but the base of VMs will have grown to 58 million, a 10-fold leap. By that time, Gartner believes, Microsoft will hold 27 per cent share, Citrix 6 per cent, Red Hat 2 per cent and others about 1 per cent.

Small enterprises will be "looking at a much more level playing field," Bittman said. He said each of the VM software providers have ways to distinguish themselves in both features and prices, but for many the big question will likely be, "Should I choose VMware or Microsoft?"

VMware, which can boast higher density and a mix of operating systems support and maturity in features, costs more than other offerings, such as Microsoft's HyperV. As it begins to release improved VM software, Microsoft seems poised to achieve growth in the SMB market, Gartner believes.

Bittman said the migration from physical servers to virtualized ones is also tied to the revolution in cloud computing, where enterprises will be considering various strategies from private clouds to public cloud services and a hybrid model. The choices for an in-house virtualization platform that enterprises make now and in the near future are likely to influence their cloud-computing choices, too, Bittman pointed out.

Virtualization is "not a commodity," Bittman noted. There's no commonality in the switching or management at this point, and mixing and matching among VM vendors is not a likely choice at this point. But he noted virtualization provides dynamic provisioning, potential for disaster-recovery support, as well server consolidation, and "it's becoming the default" for the enterprise over the next few years.