That leads to efficiency of operation. It also leads to ease of maintenance. KVM remains in step with the kernel more easily than if kernel maintainers have to make sure two different schedulers and memory managers are in sync, despite changes to one or the other.
I was talking to Brian Stevens, CTO of Red Hat, about Red Hat's next virtualization moves when he was in San Francisco for a cloud computing conference Feb. 18. He had to say no comment on when KVM would become part of Red Hat Enterprise Linux. In the past, Red hat spokesmen have said look for its adoption by RHEL 6.0. This morning he and Navin Thadani, Red Hat director of virtualization, confirmed in a teleconference that KVM will become part of the next release of Red Hat Enterprise Linux 5.4. Red Hat will fill out its virtualization product line over the next 3 to 18 months, they said.
The update to RHEL should occur on the short end of that time frame, I would guess. A long delay will postpone other KVM-dependent products.
If KVM already is part of the Linux kernel, why would Red Hat customers need to wait for it to be added to their enterprise version? The enterprise versions from both Novell and Red Hat lag behind kernel updates, which occur independently every 3 to 4 months. (Both Novell and Red Hat included KVM in the more frequently released community editions of their code.
KVM was submitted to the kernel in the fall of 2006 and incorporated into an early 2007 kernel release.
When the Linux kernel developers accepted Qumranet's submission of KVM, they said its 12,000 lines of code fit easily into the kernel. I thought KVM being added to the Linux kernel by Linus Torvalds and Andrew Morton in the fall of 2006 was an example of the revamped Linux development process. That process has proved able -- so far -- to incorporate new features rapidly while preserving the kernel's maintainability. That process was highlighted in an Oct. 22, 2007, InformationWeek cover story, How Linux Is Testing The Limits Of Open Source Development..
But it was a small Israeli company, Qumranet, that originally saw the advantages of a hypervisor inside the Linux kernel. Moshe Bar was one of its founders. He also was a founder of XenSource, and saw the friction that Xen generated with the Linux kernel developers. He concluded that Xen wasn't going to make it into the kernel and left XenSource to found Qumranet, where he commissioned the creation of KVM by Avi Kivity. Two years after KVM had been submitted to the kernel process, Qumranet was acquired by Red Hat for $107 million.
The incorporation of KVM was a landmark change for Linux. Now it, too, could make use of the virtualization hooks that Intel and AMD were putting into their chips. Xen made use of them, but Xen was outside the operating system's kernel, and there would always be a layer of chatter between it and the hypervisor to keep everything operating.
Red Hat Enterprise Linux will soon be roughly on an equal footing with Microsoft's Windows Server 2008 in terms of offering virtualization as a feature of the operating system. As if each knows they must hurry before VMware runs away with the market, the two of them agreed to support each other's operating system as a guest in their own virtual machines.
This opens the door for small and medium-sized businesses to walk with virtualization before they run. They can make use of it as it comes through the door in their familiar operating system. Both Red Hat and the Microsoft/Citrix alliance will add management capabilities on top of that operating system feature. And they hope that some of the crazy appetite to virtualize will migrate their way.