Citrix CTO and longtime Xen proponent Simon Crosby said he is unfazed by Red Hat's decision to drop the Xen hypervisor from its enterprise Linux software and focus its virtualization efforts around the KVM (Kernel-based Virtual Machine) hypervisor. Crosby claims the move won't harm Xen's standing in the virtualization market.
"To be perfectly honest it's a relief," said Crosby, who was CTO at XenSource before the virtualization vendor was purchased by Citrix. "Look, KVM is a simple way for a distro to pick up virtualization. It's just a driver in the kernel. So it's natural for a Linux distributor to put it in, it's straightforward."
Xen doesn't need special standing within Linux distributions because it goes well beyond what Crosby calls the simple virtualization capabilities of the KVM hypervisor, which has been included in Linux since 2007. Xen is more technology-agnostic than KVM, Crosby said during an interview this week at the Interop Las Vegas tech conference.
"The key is, we're not fighting an operating system's battle," Crosby said. "We're not trying to say Linux is better than Windows or vice versa. The choice of what operating system you want to use is up to you and your app. I don't have a stake in that battle. My job is to provide a wafer-thin layer that virtualizes compute, storage and networking, and gives you granular control, multi-tenancy and does a fabulous job in performance. Beyond that, I don't care."
Citrix is fighting VMware for customers in the emerging virtualization market with XenServer, based on the Xen open source hypervisor.
KVM is a relative newcomer in the open source portion of the virtualization market, but has had a few notable successes. IBM and The Planet have each built cloud computing services using KVM, with Planet officials arguing that KVM is simpler to use than Xen and will ultimately surpass Xen in popularity.
More recently, Red Hat dropped the Xen hypervisor from Red Hat Enterprise Linux, going solely with KVM. Red Hat's use of KVM had been increasing over the past two years, and the company said it was duplicating efforts by maintaining two hypervisors.
Crosby says Xen was never intended to be part of the Linux kernel, so it's natural for a Linux distributor to switch to a virtualization technology that is embedded in the kernel.
But Crosby doubted customers will leave Xen for KVM en masse, saying that XenServer will be used on 250,000 servers this year alone. Xen's virtualization management tools are superior to KVM's, he argued.
"KVM is just an ability to virtualize the CPU and memory," Crosby said. "It doesn't do networking or storage. It's the rest of the infrastructure that you build around it that turns it into something more useful."
Red Hat's implementation of KVM is still weak compared to virtualization infrastructure platforms from Citrix, VMware and even other vendors such as Oracle, Crosby said.
"I don't have any issues with KVM as a technology," he said. "It's fine. It's maturing, but it's going to take time to get there, like everything else does."
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