We reported Jan. 2 that 96% of IT managers polled by Sage Research reported running Windows on their virtualized servers and 52% reported running Linux. Without a lot more information, exactly what that means can be debated, but I think it means Windows runs on a lot of physical servers.Sage Research is the technology practice of a Boston custom market analysis firm, Chadwick Martin Bailey. The poll, as reported in the Sage/CMB Pulse newsletter recently, was a relatively small one of 126 IT decision makers at companies with 1,000 or more employees.

Some readers have expressed skepticism that the results are skewed in Microsoft's favor and the story's conclusion, "Microsoft stands to gain from the marketplace's rush to virtualization," even though it's late getting its Hyper-V hypervisor to market, must be wrong.

I don't think the results are skewed, but I can see where there's a good question about what they mean. The poll was a simple-minded one. What operating systems are you running on virtualized servers? If nearly everyone answers Windows, that's a reflection of how many Windows servers there are out there. Many of them are running a single application on a powerful x86 server, leaving lots of CPU cycles unused. That makes them a prime candidate to be consolidated onto a virtualized server.

But the main point is, no matter how much you read about Linux and the Macintosh, Windows servers are continuing to infiltrate the data center and line-of-business units at a rapid pace.

Different breakdowns of operating system market share are available, but consider this one from StackSafe, a company that produces software that examines the software stacks in IT operations and tests changes to them before they go into production. In a study of 400 IT sites, Windows Server (Windows Server 2000, 2003, and Windows NT) is the primary platform for newly deployed, multitier applications in 68% of the cases, "despite widespread attention to other alternatives."

There's no surprise to this. Data centers are rapidly evolving toward two server operating systems: Windows and Linux. Many partisans think every Linux installation is a victory vs. Microsoft, but it's long been my belief that Linux is replacing a Unix server more often than a Windows server. The only competitive factor at play, for those who don't want Microsoft to take over the whole world, is that the Unix server didn't become a Windows server.

At many IT shops, Windows skills outstrip Unix and Linux skills, although I think that picture is slowly changing. Nevertheless, if the world is rushing to virtualization, then many virtual machines will be running Windows, even though Linux lends itself to several advanced forms of virtualization on the server.

The wonder isn't that Linux was cited by only 52% of respondents but that it was cited by so many. In the StackSafe survey, Red Hat Linux, the operating system that came in second to Windows Server, showed up on "just over seven percent of servers." And that suggests that Linux is running more than its traditional share of the data center when those servers take the form of virtual machines.

But the Sage data doesn't go deep enough to answer the question in depth.