V-sprawl, as it's called, is "the biggest problem facing virtualization today," said Edward Haletky, a consultant and author of the book VMware ESX Server in the Enterprise: Planning and Securing Virtualization Servers. He added that V-sprawl raises security issues because companies may have virtual machines that haven't been properly secured. For systems administrators, Haletky said, "it's very hard to manage things when you don't know anything about it."
Although revenue numbers clearly point to VMware as the continued market leader, they don't tell the entire story of what's happening. Market-research firm IDC has been tracking license growth, which includes hypervisor licenses that are given away for free. John Humphreys, an IDC analyst, said that virtualization licenses doubled from 2006 to last year, topping the one-million mark, and that the license count grew by another 35 percent in this year's first quarter.
In 2006, VMware's license market share was 54 percent, according to Humphreys. Last year, he said, the company's share went down to 49 percent. Strictly from a licensing perspective, Microsoft, which introduced its first virtual server product in 2005, has been holding the number-two spot, with a 27 percent market share in 2006 -- a number that declined to 20 percent last year and was still heading down earlier this year, Humphreys said. But, he added, "the expectation is that Hyper-V will change that direction."
Next in line after Microsoft is Parallels, with a license share that is in the low double digits, according to Humphreys, who said that VMware's ability to retain the top spot in the future will be contingent on it maintaining a technology lead and continuing to innovate.