Red Hat and Novell sparred once again over the market readiness of the open-source Xen engine at LinuxWorld.

Red Hat insists Xen still isn't ready for prime time, which may push back the release of its Red Hat Enterprise Linux (RHEL) 5 platform until early 2007.

Red Hat executives said the Xen code in the Raleigh, N.C., Linux distributor's upcoming RHEL 5 works, but they won't advise enterprise customers and ISVs to deploy it until unfinished business around the API set, interoperability interfaces and Xen's integration with the Linux kernel are resolved.

At an informal Red Hat gathering at during LinuxWorld, Red Hat CTO Brian Stevens told CRN the RHEL 5 beta will be released in September and a release candidate will follow in the fall. He said RHEL 5 remains on track to ship by the end of the year, but Red Hat has no problem delaying its release until early next year if the Xen layer isn't ready.

"I don't care if we're first [to market] or not," Steven said, noting he would steer customers in the direction of VMware if Xen is modified. "Look, Xen is the driver [of RHEL 5]. We just want to make sure it's ready and our partners won't have to recertify or retest their offerings."

Red Hat executives noted that neither XenSource, the commercial spinoff of the Xen open-source project, nor Virtual Iron Software, another Xen-focused commercial player, has shipped its first Xen platforms. And they hinted it's because Xen interface integration with the Linux kernel and other interfaces to enable interoperability isn't complete.

Novell recently disputed Red Hat's contention that Xen isn't ready for prime time. The Waltham, Mass., software vendor, which rolled out its Xen-enabled SUSE Linux Enterprise 10 platform three weeks ago, claims that Red Hat is maligning the state of Xen and is trying to cripple its efforts on the virtualization front.

At LinuxWorld, held this week in San Francisco, Novell executives trotted out Nationwide Insurance as one customer that has opted to deploy Novell's virtualization solution on IBM mainframes. Also, during a press conference, Novell executives insisted that Red Hat retracted its earlier statement that Xen wasn't ready for prime time.

"We're first to market with Xen virtualization, and it's been battle-tested and ready for prime time," said Roger Levy, vice president of open platform solutions at Novell.

John Dragoon, senior vice president and chief marketing officer at Novell, said Red Hat didn't question Xen's readiness when it announced its plans for integrated virtualization in RHEL 5 last spring.

"Red Hat's comments are suspect because they don't have something ready for prime time. We do," Dragoon said. "A Red Hat press release in March said Xen was ready."

In that release, Red Hat said it would make its Virtualization Migration and Assessment Services and Enterprise Virtualization beta available this summer. It also said the following: "Red Hat Enterprise Linux v. 5, scheduled for general availability by the end of 2006, will feature fully integrated virtualization."

At LinuxWorld, XenSource and Virtual Iron said they plan to ship their respective XenEnterprise and Virtual Iron platforms in the next few weeks. They indicated that Xen is ready.

Xen works on Novell's Linux distribution, XenSource said. "I know it was tested on every piece of hardware," said Simon Crosby, CTO at XenSource.

Virtual Iron, another ISV preparing to launch a Xen-based virtualization platform for the data center, said Xen is ready. Virtual Iron's solution will ship in the September-October time frame, said Mike Grandinetti, chief marketing officer for the Lowell, Mass.-based company.

"I'm not sure why Red Hat is saying [Xen is] not ready," said Alex Vasilevsky, founder, vice president and CTO of Virtual Iron. "We believe it's ready. We'll start taking orders soon."