Ubuntu bucks trend, goes for KVM virtualisation

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

Red Hat Enterprise Linux and Novell's Suse Linux Enterprise Server both use the Xen virtualisation 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 virtualisation focus," Soren Hansen, the Ubuntu Server Team's 26-year-old virtualisation 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 virtualisation ball. Virtualisation is making its way into datacentres and onto developer workstations everywhere. Even 'regular' users are using it to run Ubuntu on Mac OS X all the time," Hansen said. "Virtualisation 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 virtualisation product, called Hyper-V. However, the market leader for virtualisation is EMC subsidiary VMware, which sells not only the virtualisation 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' virtualisation and management division, said KVM's approach is better suited to desktop machines than to servers.

"Ubuntu is not widely deployed in enterprise datacentres, 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 virtualisation model makes sense to them".

Although Ubuntu didn't use the same virtualisation 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 virtualisation 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.