Is Linux growing at Windows' or Unix's expense?

Recent survey data reveals that Linux figures prominently in data centers, but it's unclear whether Linux has grown at the expense of Windows or of legacy systems.

Windows may be king of data centers, but Linux has a foothold in nearly every courtyard and is sure to make further

inroads in the year ahead.

For more on the Data Center Decisions 2008 survey:
Server purchasing reveals virtualization 's imprint

CMDBs gain favor in 2008 data center budgets

Data center energy a concern, but metrics lacking

Virtualization goes mainstream, warts and all

According to the Data Center Decisions 2008 Purchasing Intentions Survey, 91% of data centers run Microsoft Windows, but a large percentage also use Red Hat Enterprise Linux (48%) or Novell SUSE (21%, multiple versions) in their data centers. Nonetheless, Linux use remains limited in scope, with two-thirds of respondents running Linux on 25% or less of their servers, with application servers the most common pairing.

But Linux use could be on the upswing: 47% of respondents said they would use or evaluate Linux in the coming year, with lower cost as the primary driver. But the largest percentage said they had no further plans to migrate from Unix to Linux, indicating that future Linux growth would be at the expense of other platforms. In response to a different question, 23% said that whenever possible they would migrate from Windows to Linux, and another 16% said that to avoid a Windows upgrade, they would migrate to Linux.

Also expanding Linux use in the data center is a sharp projected upswing in use for its built-in virtualization. Although Red Hat and SUSE Xen-based virtualization tally only about 2.5% apiece of deployments currently, respondents' projections for the technology climb steeply to 10% for Red Hat and 5% for SUSE over the next year.

Finally, Linux use for mission-critical apps remains about the same as last year, with 33% using Red Hat, and 12.5% using SUSE.

Linux growth at whose expense?
George Weiss, the vice president of Stamford, Conn.-based Gartner Inc., said that there is probably "a whole lot more Linux [in use] than people realize" because so much is downloaded for free that is not counted in server shipments. Although the survey did not break down Linux use by organization size, Weiss speculated that Linux may be used in 80% of large enterprises, with lesser percentages in smaller businesses.

Contrary to the survey results, Weiss believes that companies have continued to migrate off Unix in large numbers as well as off Solaris Sparc servers and RISC processors, so all migrations to Linux are not at Windows' expense, Weiss said. And the fact that most organizations run Linux on 25% or less of their total number of servers is not surprising since many servers run legacy systems, he said.

Relative to legacy systems, Linux's growth is buoyed by survey data. Sixty-three percent of shops will increase their spending on Linux-based systems this year, compared with at most 39% increase for legacy Unix, iSeries and mainframe systems.

Michael Coté, an analyst at Denver, Colo.-based research and consulting firm RedMonk, concurred that Windows remains dominant in the data center, despite the growth of Linux, but that Linux is benefiting, even for mission-critical applications, from growing confidence in the platform and the recognition that Linux is not a "kooky operating system."

Charles King, principal analyst at Hayward, Calif.-based Pund-IT Inc., said replacement of Windows with Linux has become easier in recent years as Linux has become more user-friendly. A remaining hurdle, however, is the application gap between Windows and Linux, he said.

The virtualization wild card
Virtualization is a natural driver for Linux, King added. As companies virtualize and consolidate, they are also more likely to replace proprietary software to reduce licensing costs as part of the change, he said.

"The ideal state of the data center is to do nothing," added Coté. By initiating change, virtualization has created a window of opportunity for migrations to Linux, he said.

Weiss said the survey's low estimates for open source virtualization jibes with Gartner's estimates. Linux vendors can't match VMware's management offerings, although Novell's PlateSpin and ZenWorks Orchestrator applications give it the edge over Red Hat, he said. Yet Red Hat's high-volume installs are prohibitively expensive, license-wise for Novell to displace, he said.

The Gartner analyst predicted that Linux-based virtualization will peak in 2010. He also expressed puzzlement at Red Hat's strategy in switching its primary focus from Xen to KVM, which he said lacks a "mature production environment." Supporting both hypervisors would require a data center to add a central management console, he added.

Coté added that when it comes to the growth of open source virtualization, the biggest unknown is the impact of Microsoft's Hyper-V.

"Microsoft is the biggest player, so people will want to wait and see what Hyper-V has to offer," Coté said. "Until that's decided, Microsoft is a bottleneck."

For SearchDataCenter.com's entire survey report, click here.

Let us know what you think about the story; email Pam Derringer, News Writer . And check out Enterprise Linux Log.

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