Sun Microsystems is presenting a challenge to Red Hat with competitively priced support in an update of its Solaris 10 operating system, announced Tuesday.

Open-source Solaris 10 11/06 comes with support subscriptions at what Sun says is half the price of a comparable support plan from Linux distributor Red Hat. Red Hat, the largest Linux distribution provider, has faced support price pressure from others, most notably a deal announced in October 2006 by database software company Oracle. Microsoft in November aligned with Novell, a rival Linux distributor to Red Hat.

"It's obvious that Sun is gunning for Red Hat," said Jonathan Eunice, founder of the technology research firm Illuminata. Solaris is a Unix-based operating system also available for free, though Sun charges for support. Linux distributors adopt a similar business model.

Sun's Solaris annual support contracts range from $240 to $1,180 for one- or two-socket x86 servers, depending on whether the buyer chooses the "basic" or "premium" plan. Sun's basic plan costs about 40 percent less and the premium plan about 50 percent less than comparable Red Hat plans, said Sun spokesman Bob Wientzen.

Red Hat's Web site lists Red Hat Linux ES basic for $349 per year per system and Red Hat Linux AS premium for $2,499. A Red Hat spokesman did not return calls and an e-mail requesting comment, but after Oracle's move last fall, Red Hat chief executive officer Matthew Szulik said Red Hat would not lower its prices due to a competitor's price cuts.

Pricing its support below Red Hat's is "a volume play," said Eunice, so that Solaris can gain market share against competing operating systems.

The new Solaris is available as a free download from Sun's Web site and can run on Sun x86 servers as well as servers made by Dell, HP, and IBM.

The most notable improvement in the operating system, Eunice said, is the Solaris Clusters feature for business continuity and disaster recovery, which was announced Jan. 9. Clustering makes it possible for servers to work together so that if one server fails, the workload can be quickly moved to another server. The previous version of Solaris Clusters didn't work as well on x86 processor platforms as on Sun's own Sparc platform, but the upgrade fixes that shortcoming.

"Sun has made enormous strides. This is a rockin' product now," Eunice said.

Meanwhile, Sun's Wientzen declined to confirm media reports that Sun is going to license open source Solaris under the GNU GPL (general public license) as it did with its Java programming language. "We are not ruling it out, but we have no announcement about that today." he said.

On the virtualization front, Solaris 10 11/06 now supports the Xen hypervisor, an open-source software interface for virtual machines. Virtualization refers to the ability of a server to run multiple operating systems and software applications simultaneously. Sun's Logical Domains and Solaris Containers features make it possible for a server to run as many as 32 different operating systems on a Sun server powered by Sun Sparc 11 processors.