So the standardization that's usually supplied by an open source project gives way with Xen to vendor lock-in initiatives. The cross hypervisor management vendors are quite careful and specific when they say they support Xen -- they almost always mean XenSource's XenServer -- as the most likely candidate to succeed in the marketplace, and not all the other variations.
Nevertheless, Xen, and in particular XenSource as part of Citrix, have a big head start over KVM and Qumranet in terms of winning desktop virtualization followers. XenSource now has Citrix's credibility behind it in terms of being able to scale up to thousands of end users quickly. Citrix has many years of supplying a connection broker for its Presentation Server. Every desktop virtualization vendor needs a connection broker -- hundreds or thousands of end users are likely to call for virtual desktops or application services at the same time. The connection broker manages the traffic within acceptable response times.
Qumranet's SolidICE product line has its own connection broker, and throws in the wrinkle of allowing end users to customize their desktops without IT intervention. If a user wants to add an application, Qumranet checks the addition and adds it to the user's virtual desktop, provided it doesn't break any the guidelines or policies governing that end user's group. The next time he activates his virtual desktop, the new application will be there.
That may or may not give it a competitive talking point against XenSource's XenServer. But what about VMware and its Virtual Desktop Infrastructure? It's out there with a lot of its own bells and whistles and the aggressive support of the leading virtualization vendor.
"Qumranet lies squarely in the path of both VMware and Citrix," concluded the 451 Group's virtualization analyst, Rachel Chalmers, as she took a look at Qumranet before it joined the ranks of Red Hat. It still does after the acquisition.
Red Hat's one prospect is to exploit the efficiencies inherent in the hypervisor engine being part of the Linux kernel and hope that it's to ease-of-use and performance advantages for Qumranet's SolidICE desktop product.
KVM was the only hypervisor to win acceptance as part of the kernel. Xen beat its head against the door of the kernel development process but never quite mastered how to integrate Xen into that the methodology of that process. (For one thing, kernel developers like minimum disruption of existing kernel functions when they add code to minimize the need for repeated future maintenance. Xen needed kernel adjustments; KVM didn't.) Simon Crosby, CTO at XenSource, can still drop a reference to the "surly members of the open source community" without batting an eye.
So KVM is inside the kernel, and has the potential to virtualize either Linux or Windows desktops. For now, it's only doing Windows--virtual machines running Windows 2000 or Windows XP, says Red Hat's Mike Ferris and Katrinka McCallum.
KVM may be in the Linux kernel used by open source developers, but it's not yet in Red Hat Enterprise Linux; that will likely come with Enterprise Linux version 6.
So KVM exploit's the kernel's memory management, scheduling, and other functions, blending into the heart of what's becoming the workhorse of the Internet, the Linux server. Is that enough to make Red Hat a successful desktop virtualization vendor? Too soon to say, but Red Hat certainly has its work cut out for it.