On the third point, Microsoft's System Center Virtual Machine Manager can't run on a cluster of servers, Wolf said. "Microsoft will argue that you can put it in a virtual machine and fail the VM over [to another server], but that's not the point; it can't be made fault tolerant," he said.
Nevertheless, the upcoming Hyper-V release has some significant enhancements, including live migration of virtual machines; cluster shared volumes; support for third-party cluster file systems; hardware-assisted memory virtualization, and virtual storage hot-add, Jones said.
The company also does better than Citrix on the list of features Burton Group considers "preferred" but not required. Hyper-V will lack 14 of the 42 preferred features, while XenServer lacks 17 and VMware seven. The picture is similar for "optional" features.
Microsoft responded to the findings by highlighting customers that it says are using its product. “Our customers have their own scorecards, and Ingersoll Rand, Jackson Energy Authority, and the University of Miami have experienced success and cost savings through using our products,” the company said via email.
Burton Group found at least one "preferred" feature that both XenServer and Hyper-V have, but which VMware lacks: virtual storage disk compatibility. "VMware is proprietary; it doesn't support other hypervisors," Wolf said.
Burton Group presented its findings at a VMworld session entitled "Hypervisor Competitive Differences: What the Vendors Aren’t Telling You."
It's hard for customers to compare vendors' products using their data sheets because each tries to make its products look best, and sometimes the vendors say they have a certain feature even if it is poorly implemented, Jones said.
Even Glemmestad, an IT engineer with Norwegian agricultural supplier Felleskjopet, said Burton Group's assessment made sense to him. He'd read that the analyst firm considers XenServer production-ready but came to the session to find out on what basis.
His company mainly uses VMware, but it is considering XenServer to virtualize their XenApp servers, he said.