KVM steals virtualization spotlight

A new open-source virtual-machine project has quickly won Linux allies, but its arrival brings complications.

Four months ago, almost nobody had heard of an open-source virtualization software called KVM. But that was then.

The project, backed by a stealth-mode start-up called Qumranet, uses a technical and cultural approach that has quickly drawn powerful allies--including Red Hat and Linux founder Linus Torvalds.

That success is only a first step in KVM's push to make a mark in virtualization. But it signals significant influence over the technology, which is spurring a top-to-bottom revamp of the computing industry through its ability to make a single machine behave like many.

But does the world need another virtualization option? EMC subsidiary VMware rules the roost today. Microsoft is working on a project, called Viridian, that is set to debut in roughly a year. And numerous open-source allies already have focused attention on an open-source rival called Xen. While KVM delivers some new options and competition, it also brings new complications.

"In the near term, KVM will cause some pain because of the market confusion and developer dilution it will cause," said Illuminata analyst Gordon Haff. "But in the longer run, better technical options can only be good for Linux and open source."

KVM, which stands for "Kernel-based Virtual Machine," provides a new Linux-based mechanism for splitting a single physical computer into multiple virtual machines. It's going up against another approach, which uses a low-level software "hypervisor" to perform the same virtualization function.

The industry is scrambling to adopt virtualization for a range of reasons: so that groups of inefficient servers can be replaced with a fewer machines; so software can be tested in harmless partitions; and ultimately, so data centers packed with computers can fluidly adjust to shifting priorities.

Industry players such as Novell and IBM say they're watching to see how well KVM fares. But Brian Stevens, the chief technology officer of dominant Linux seller Red Hat, believes KVM is viable.

"There's a year of work, I'd guess, to really make it at parity to where Xen is today...But I think it's going to happen," Stevens said. "The (open-source programming) community is really going to gravitate (to KVM) much more so than (to) Xen."

Qumranet has funding from Sequoia Capital and Norwest Venture Partners, but Chief Executive Benny Schnaider is mum on the company's business plan. In an interview, he said only that Qumranet is "not planning to make money by selling or supporting KVM."

We did things the Linux way.
--Avi Kivity,
lead programmer of KVM

The KVM project got started in early 2006, Schnaider said. That's about the same time that Moshe Bar left XenSource, the Xen commercialization start-up that he co-founded. Bar, who now is Qumranet's chief technology officer, declined to comment for this story.

Qumranet is based in Santa Clara, Calif., with research and development in Israel. (Qumran is an ancient settlement near the caves where the Dead Sea Scrolls were found.) The start-up has more than 30 employees, most of them engineers, Schnaider said. Given that fewer than a dozen are working on KVM, according to lead programmer and Qumranet employee Avi Kivity, it's a good bet that the company has other technology in the works.

Kivity . His patch updated Linux so that higher-level software could take advantage of hardware virtualization features built into the latest processors from Intel and Advanced Micro Devices. The result: Other operating systems, including Microsoft Windows, can be "guests" running on a Linux host foundation, on newer hardware.

KVM's approach differs from that of Xen, which governs access to hardware using a combination of a lightweight "hypervisor" foundation and a privileged operating system, which is typically Linux.

KVM's method is conceptually closer to one of two approaches used by VMware--the "hosted" model used in the free VMware Server and Player products. In that model, guest virtual machines run atop a copy of the operating system. In the second VMware approach, used in the higher-end ESX Server product, a full-featured, heavyweight hypervisor governs access to underlying hardware.

Unlike Xen additions to Linux, the KVM patch slipped nearly instantly into the mainstream kernel maintained by Torvalds and a group of deputies.

"We did things the Linux way," Kivity said in an interview. "I am a longtime lurker on the Linux kernel mailing list, so I know what's important to the kernel maintainers and tried to get things right the first time. Where I got things wrong, I fixed them quickly."

He introduced KVM with source code, not words. "Kernel maintainers only take you seriously if the first word in a message is 'PATCH,'" Kivity said.

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