Xen vs. KVM: round 1 bell to ring soon

Industry executives are downplaying concerns about a growing schism between rival open source virtualization factions but a market battle between Xen and KVM appears increasingly likely, and imminent. 

At the San Francisco, Calif. conference this week, Qumranet, a Santa Clara, Calif-based commercial startup that funds KVM, told ZDNet that the company’s first product will be unveiled in late September and will ship in the fourth quarter.

It won’t be a knock off of rival XenSource’s XenEnterprise. Because it leverages the KVM support in the Linux kernel, the new offering can focus on advanced services such as storage virtualization, hinted Qumranet co-founder, president and vice president of R&D, Rami Tamir.

Qumranet’s president agreed that the two platforms are supported by the Linux kernel and that customers will have access to glue code to make them interoperable. But will it be a peaceful co-existence?

Tamir offered up some fightin’ words. “Being latecomer is an advantage,” Tamir claimed, then lowered the volume of his voice. “Xen is going away.”

From the standpoint of industry executives, that’s just marketing mantra.

Linux kernel maintainer Andrew Morton said customers need not fear fragmentation or backing a project that fails. Kernel.org supports all viable open source virtualization engines and will continue to do so. “No,” Morton said, when asked by an attendee at LinuxWorld about possible fragmentation. He said customers won’t be caught in the crossfire “because we merged [open source virtualization engines] all with the kernel.”

"Xen and KVM are in bare distributions. Virtualization is all done. It took a long time to get virtualization [done],” Morton said during his keynote Monday. “I don’t see why that would introduce problems. [Distributors] can select which one to support and provide to customers."

Kernel-based virtual machine (KVM) is a Linux kernel infrastructure that supports virtualization. It offers  full virtualization using Intel VT or AMD-V hardware assist and limited support for paravirtualization for Linux guests and Windows.

Xen is also supported in the kernel. In July, Linus Torvalds merged the XenSource patches into upstream for release as part of the 2.6.23 kernel, XenSource's blog reported.

 Xen has a big lead over KVM to date. Xen is integrated into the two leading Linux distributions and the commercial spinoff the Xen open source project, XenSource, recently signed its 500th ccmmercial customer. The Palo Alto, Calif, company is preparing to launch a major upgrade of its platform, XenEnterprise 4.0, in late August that offers advanced management features as well as storage and server virtualization features based on its partnership with Symantec.

Heavy duty Linux user Amazon.com is a big backer of Xen but the collective power of the Linux Foundation and others who back open source virtualization will not allow an API war like those seen in the proprietary software industry, said Dr. Werners Vogels, vice president of worldwide architecture and CTO of Amazon.com told ZDNet at a LinuxWorld party.    Executives from Red Hat and Novell, whose Linux distributions incorporate Xen, said they will ensure that customers have interoperability code to support all engines. Red Hat, for example, launched an open source virtualization API project called Libvirt to ensure interoperability of various virtualization mechanisms. It currently supports Xen, KVM and Qemu.

“It’s a wild west scene right now on virtualization,” said Mike Evans, director of business development at Red Hat, during an interview at LinuxWorld Tuesday. He said Red Hat launched the open source project that abstracts the end user from seprate libraries and mechanisms. “Libvirt is a set of APIs that allow us to plug in different virtualization engines. We’re shielding the user.”

At a Novell dinner Tuesday night, Novell CEO Ron Hovsepian and CTO Dr. Jeffrey Jaffe said the company is developing virtual machine monitoring and management capabilities and an interface layer to ensure that SUSE Linux Enterprise Server customers and ISVs can have a choice of which engine to use and still be assured of an “interoperable" Linux. “Any fragmentation would benefit Microsoft and we don’t want to do that,” Jaffe said.

Following a conference session detailing the merits of Xen and KVM, Qumranet’s Tamir acknowledged that several efforts are underway to enable interoperability. He noted that while one IBM programmer is working on code to add para virtualization features to KVM, and thus make it more competitive with Xen, still others at IBM are developing a CIM-based module that will ensure both engines will be supported and managed according to industry accepted  management standards.   Still, uncertainty about which open source virtualization engine will dominate could likely stall corporate adoption.

Proprietary virtualization software kingpin VMware is not averse to a battle among open source rivals but would prefer it if there were no competitors at all, quipped Mendel Rosenblum, founder and CTO of VMware, after his  keynote presentation on Thursday.

By his estimation, it’s inevitable that Xen and KVM are headed for war but he was skeptical about interoperability promises, Rosenblum told ZDNet.   “There will be a battle of open source virtualization engines,” he said. “I think one of the issue for both [Xen and KVM] is that current hardware support for virtualization doesn’t recurse very well so if you try to run KVM inside Xen virtual machine it doesn't work and I don’t think it’ll work soon with any kind of acceptable performance. Obviously, on the same box you probably are not deploying both technologies.”