Citing quality concerns, Viridian will not include Live migration, or hot-add resources for storage, networking, memory and processors, which allow developers to move, add or remove resources without taking the machine down, and it will limit support to 16 cores, or four quad-core processors.
"The focus for the release of Windows Server virtualization is quality and timeliness," Microsoft said in a statement. "To meet those objectives, Microsoft has made some hard decisions and now plans to defer some features to a later release."
"Good news or bad news, we feel it's necessary to update our customers on what's going on," he said.
Mike Neil, general manager of Microsoft's virtualization strategy, wrote on his blog Thursday that for "all the progress comes the occasional trade-off."
Neil explained that Microsoft wanted to spill the news to the public so "no one is surprised at WinHEC when we demo all the other innovations in Windows Server virtualization."
WinHEC 2007, the Microsoft event for hardware engineers building to Windows, kicks off next Tuesday in Los Angeles. Microsoft first demonstrated Viridian and released technical content of the new architecture at last year's WinHEC show.
Illuminata analyst Gordon Haff said the latest setback does not look good for Viridian.
"Microsoft is already behind and now they're seemingly scaling back features like Live migration that are basic table stakes," Haff told internetnews.com via e-mail. "At the end of the day, Microsoft's customers can continue to use VMware and Xen-based products. But maybe Microsoft needs to start partnering with, rather than fighting, these products."
Microsoft describes Viridian as a thin software layer between the hardware and the Windows Server Longhorn operating system that will allow several operating systems to run on a host computer at the same time.