Ubuntu picks KVM over Xen for virtualization

Heading in a different direction from its main rivals, Ubuntu Linux will use KVM as its primary virtualization software.

Red Hat Enterprise Linux and Novell's Suse Linux Enterprise Server both use the Xen virtualization software, a "hypervisor" layer that lets multiple operating systems run on the same computer. In contrast, the KVM software runs on top of a version of Linux, the "host" operating system that provides a foundation for other "guest" operating systems to run in a virtual mode.

"We've chosen to settle on KVM as our main virtualization focus," Soren Hansen, the Ubuntu Server Team's 26-year-old virtualization specialist, said in the Ubuntu Weekly News.

The move gives new prominence to KVM, which was initially popular with Linus Torvalds and other programmers of the Linux kernel. However, in the months since start-up Qumranet began the KVM project, the Xen programmers have made more progress in dovetailing their code more closely with the Linux kernel. KVM and Xen both are open-source packages.

KVM will be built into Ubuntu's next version, called Hardy Heron and due in April. "For the Hardy Heron release, we've really picked up the virtualization ball. Virtualization is making its way into data centers and onto developer workstations everywhere. Even 'regular' users are using it to run Ubuntu on Mac OS X all the time," Hansen said. "Virtualization has been on our agenda for a long time, but it became a top priority at UDS (Ubuntu Developer Summit) in November. We could see that demand for it was growing."

Canonical, the commercial sponsor of Ubuntu, will provide long-term support for Hardy Heron that lasts five years for servers and three years for PCs. Ubuntu is updated about every six months, but Hardy Heron is only the second version to get long-term support.

Xen is already built into Red Hat and Novell's Linux products, and Microsoft is on the brink of releasing its own virtualization product, called Hyper-V. However, the market leader for virtualization is EMC subsidiary VMware, which sells not only the virtualization foundation but also higher-level tools to monitor server performance and to move applications from one server to another to adjust work load.

Hansen said programmers also evaluated several other options, including Xen, Parallels' OpenVZ, KQEMU, and VirtualBox. "We found that KVM was the best fit for us right now."

Unsurprisingly, Xen fans see things differently. In particular, Simon Crosby, chief technology officer of Citrix Systems' virtualization and management division, said KVM's approach is better suited to desktop machines than to servers.

"Ubuntu is not widely deployed in enterprise data centers, where the need for a comprehensive virtual infrastructure layer independent of any guest operating system...is a requirement articulated by every customer," Crosby said in a statement. Ubuntu is widely used on desktops, so for Ubuntu programmers, "it seems natural that a hosted virtualization model makes sense to them."

Although Ubuntu didn't use the same virtualization foundation that dominant Linux seller Red Hat chose, it will use the libvirt package Red Hat created to provide a neutral management interface to Xen, KVM, or other compatible virtualization systems.

To provide an easier interface to libvirt, Ubuntu will employ software called virt-manager, Hansen said. "It allows you to set up new virtual machine, see which ones are running, and how much CPU they're consuming," he said.

[HughJJorgan]

Why does it matter how old the virtualization specialist is?

"Soren Hansen, the Ubuntu Server Team's 26-year-old virtualization specialist" -- that little bit of information seems oddly placed.

[Shankland]

He shared his age, so I did too

I included his age after he did in his own self-description. You can choose to judge him or not as you like on the information, but in the media, it's common to say how old a person is or where he or she lives to add a bit more description of a subject.

[TBolt]

personal use rather than enterprise

Does this decision mean that Ubuntu developers only have their sights on the consumer market rather than the enterprise market? Is this part of the long-term strategy for the Ubuntu team?

[sorenh]

No..

We are very aware of the enterprise market as well. In fact, for our virtualisation efforts, that's the main focus. I disagree with Simon Crosby's statement that "KVM's approach is better suited to desktop machines than to servers."

It might seem to be true due to the way in which you invoke kvm and so on, but when you bring libvirt into the mix, this changes dramatically. libvirt includes a daemon that manages your kvm instances, allowing you to attach and detach from the console of your virtual machines, pause them, save their state and reload it later (or on a different machine), etc. Essentially everything you'd expect to do to your virtual machines in a production environment. If there's something you find that you need to do to make it suitable in a server environment that it can't currently do, please let us know, so that we can fix that :)

[rac171]

Actually, it's KVM and VMware

Canonical, the commercial backer of Ubuntu,
also partners with VMware. The combination of
VMware and KVM put us in a great position to
meet all the needs of our users.

Rick Clark

Ubuntu Server Team