Microsoft Still Cleaning Up With Windows

One consideration possibly putting a damper on Linux is the perception that committing to open source means paying higher staffing and management costs to support it.

"In broad, sweeping, general terms, you can find a way to configure Linux cheaper than Windows, in terms of acquisition cost," says IDC analyst Al Gillen. "But that's only one cost" to the larger issue of maintaining software systems over the three- to four-year life of a server.

While Gartner and IDC don't track server operating systems by brand, Novell(NOVL Quote) and Red Hat(RHT Quote) have commercialized the open source software. Novell sells the SUSE Linux Enterprise Server, and Red Hat sells the Enterprise Linux Server.

Servers aside, management at VMware(VMW Quote) have suggested that virtualization will ultimately undermine the need for big operating systems like Windows.

But virtualization may actually be helping Windows, which is more popular for virtualizing business IT networks because of its larger installed base, Gillen says.

"I don't think people make their operating system selection on a virtualization strategy," Gillen says. What is affected by virtualization is the choice of computer architecture. VMware is designed for what is called "x86" architecture. Virtualization, which allows fewer servers to function with more capabilities, changes the architecture decisions, Gillen says.

This could account for a drop in sales of Unix operating systems, which tend to be based on non-x86 architecture. Unix gave up 1.2% of market share, shipping nearly 20,000 fewer servers than the same quarter of the prior year and holding just 7.6% of the market, according to Gartner data. Both Sun(JAVA Quote) and IBM(IBM Quote) sell Unix-based servers. But IBM sells or supports the major operating systems, including Linux and a proprietary OS.