The initial tight relationship between VMware and Microsoft benefited both companies, Horschman said: VMware could virtualize Windows environments, which also gave it access to Microsoft clients. The two companies also have support agreements that make it easier for users to find help for their VMware-virtualized environments, he said.The key difference, Horschman said, is that Hyper-V is part of Microsoft's Windows Server 2008 operating system. Conversely, VMware is moving its hypervisor technology away from the operating system. The latest example is ESXi, released late last year, which is an operating system-independent hypervisor that can be integrated into the server or used as a stand-alone hard drive install. "It takes a huge chunk of the software out of play," which increases security around the virtual machines by separating them from the malware and other vulnerabilities in operating systems, Horschman said. "These are two fundamentally different views of where the hypervisor should go." Not so, said Jeff Woolsey, senior program manager for Hyper-V. "I would contend that [VMware's] ESX [Server] is an operating system," Woolsey said. He also said there is an advantage for users in having a virtualization hypervisor tightly integrated with the slew of capabilities Microsoft offers in Windows Server 2008. Woolsey disagreed with Horschman's assessment that Hyper-V is little more than a first-generation hypervisor, little more than what VMware was offering several years ago. Woolsey said a few dozen customers are running production environments on the Hyper-V beta, and that Microsoft itself is using the beta to run its TechNet and MSDN Web sites, which get a combined 4 million hits a day. "These have been running in Hyper-V since the beta, and there has been no problem," he said. He also pointed out there there are more than 175 servers that have been qualified for Hyper-V, and that the technology offers high-availability and failover cluster capabilities. That means if the physical server goes down, those virtual machines running on it automatically are switched to other physical systems. At this point, Woolsey said, the only key advantage VMware holds over Microsoft is the ability to migrate live virtual machines, something VMware offers in its VMotion technology. Woolsey said the live migration capabilities will be available in the next version of Hyper-V. He declined to say when that will be released. "We feel good about the performance and management" of Hyper-V, Woolsey said, pointing out that Microsoft testing showed Hyper-V outperforming ESX.
However, with Hyper-V on the horizon, the two are about to ramp up the competition knowing that they will have to continue cooperating as well. That doesn't keep the officials of either company from pointing out perceived weaknesses of the other.