Red Hat Admits Virtual Holdup in Linux Kernel

The vendor says its attempts to add Xen virtualization technology to the Linux kernel won't bear fruit any time soon.

The move to weld virtualization technology deep into the Linux kernel is stuck on the workbench.

Despite earlier optimistic predictions by Red Hat execs and others in the community that the work would take just a couple of months, they say now that the technology is still "far from ready for inclusion in the kernel."

The problem is that the Xen Projects virtualization code wont stand still for the process.

An emerging key to many enterprise consolidation strategies, virtualization lets IT managers run multiple copies of Linux on a single server.

For Red Hat, a big part of the strategy is making virtualization an integrated part of the Linux system itself, so that the kernel understands that it is virtualized and can better participate in its management.

"I am an eternal optimist, but I really did not appreciate how extensively and rapidly the Xen code is changed," Brian Stevens, Red Hats chief technical officer, told eWEEK at the launch of the companys Integrated Virtualization strategy in San Francisco on March 14.

"There are still hundreds of change sets taking place on a weekly basis, with a lot of work still left to do. While we have tried to focus less on functionality and more on stability, even with Xen 3.0, which was released in December, the code is still far from ready for inclusion in the kernel," Stevens said.

In October of 2005, Stevens took up the task of driving forward the merging of Xen into the Linux kernel, an initiative that had previously run out of steam with no one at the helm. He told eWEEK at the time that "Red Hat is now stepping forward … We would like to have the Xen virtualization technology submitted for inclusion in the Linux kernel in the next two months. I dont think its a long-term project at all."

The goal was to make virtualization and its management part of a Linux system, "so this is not just maturing the technology, but having the operating system itself, the kernel itself, be intimately aware that it is being virtualized so that it participates," Stevens said at the time.

/zimages/5/28571.gifClick here to read about why Red Hat is pushing to have Xen virtualization technology added to the Linux kernel.

However, it is now more likely that individual components of the Xen virtualization technology will be merged into the kernel over time, starting with the Xen interfaces, rather than all of it as a single submission, Stevens said.

This would also mean that the Raleigh, N.C.. company will have to support Xen "out of tree" for RHEL (Red Hat Enterprise Linux) Version 5, which is scheduled for general availability before the end of this year and will feature fully integrated virtualization.

That is because the Xen virtualization technology will not have been submitted to the Linux tree by that time, Stevens said. "Each time there is a new rev, our engineers have to merge the Linux tree with the Xen tree, and we then spend a couple of weeks on stabilizing this each time, which is a lengthy, time-consuming and painful process," he said.

Andrew Morton, the current maintainer of the Linux 2.6 kernel, who works for Open Source Development Labs in Beaverton, Ore., also told eWEEK that he was not hearing much on the Xen submission front. "I dont know what people have been doing lately—nothing has come my way," he said.

/zimages/5/28571.gifClick here to read more about the Linux kernel development process.

While pricing and packaging for RHEL 5 has not been finalized, Stevens said he does not want to force the virtualization technology on those existing customers who may not want it, so he is looking at a separate server solution product that will include the virtualization technology.

Next Page: Unlimited-use pricing model encourages virtualization.