A recent survey of 1,948 users found Windows edging out Unix as the top operating system that Linux replaces in migration projects.

Linux's presence in the data center has grown rapidly alongside Windows' -- together the two have been the fastest growing data center operating systems, frequently at the expense of Unix. Now a new survey by the Linux Foundation suggests that, at least among large Linux users, Linux is growing at the expense of Windows, too.

It's hard to get a precise picture of Linux's position in the data center. No one company owns it, and various versions are readily available through free download, which no one claims to track. The Linux Foundation turned to known Linux users, the members of its End User Council, and 1,900 other enterprise and government Linux users selected by the Yoeman Technology Group.

When Linux growth has been tracked over the past decade, much of it was attributed to migrations from the former Sun Microsystems' Solaris, IBM AIX, and HP-UX and other Unixes. In the recent survey, "migrations to Linux from Windows are surpassing those from Unix," the report said, with 37% coming from Windows and 31% from the Unixes.

It says that 76% of companies plan to add more Linux servers over the next 12 months, compared to 41% that plan to add Windows servers. Over a five-year period, the shift accelerates: 79.4% plan to add more Linux; 21% more Windows. Forty-four percent said they were planning to maintain their existing number of Windows servers, or decrease them over the next 12 months.

The survey contains the bias of being submitted to existing Linux users motivated to fill out a survey from the Linux Foundation. Nevertheless, previous foundation reports and anecdotal evidence had revealed preferences for Linux and Windows, not a favoring of Linux over Windows, its spokesmen said.

In addition, 66% say their current Linux deployments are new server deployments rather than replacements for existing systems, showing Linux is at the forefront of new application implementations. "This greenfield market-share grab is a good indicator of a platform's future performance," claimed the Yeoman Technology Group report.