A public beta version of Viridian--formally called Windows Server virtualization--was set for release in the first half of 2007, but now won't appear until the second half of the year, said Mike Neil, general manager of Microsoft's virtualization strategy, in a blog posting Thursday. And Service Pack 1 for the current Virtual Server 2005 R2 product won't appear until later this quarter; it had been scheduled for the end of March.
However, Microsoft is holding the line on the final release of Viridian and on, of which Viridian will be a part. The final version of Longhorn Server is still scheduled to be released to computer manufacturers by the end of this year, with Viridian appearing within 180 days of the operating system.
Virtualization software lets a single computer run multiple operating systems simultaneously in separate partitions called virtual machines. Doing so can let administrators replace several somewhat idle machines with one more efficiently used server and, in the longer term, create a more flexible computing infrastructure.
The technology is catching on in mainstream servers using x86 processors such as Intel's Xeon and Advanced Micro Devices' Opteron, and Microsoft is one of several competitors trying to win customers from market leader.
Virtualization means that some competitors must work cheek-by-jowl, proximity that sometimes has proved awkward. For example,, and Microsoft has worked with open-source competitor XenSource in an attempt to ensure that both Windows and Linux can run on either company's virtualization foundation.
Virtualization software is now built into the two major commercial versions of Linux,and . Both those products use the open-source Xen project.
Like Xen, Viridian is a hypervisor, software that runs at a layer between operating systems and the computer's hardware, mediating communications between the two. However, Microsoft's current software, Virtual Server and Virtual PC, run atop Windows. In that model, Windows is a "host" operating system that runs "guest" operating systems in virtual machines.
Virtual Server 2005 R2 SP1, available in beta form now and in a release candidate form by the end of April, includes several significant new features. Among them: compatibility with IVT and AMD-V virtualization technology built into newer Intel and AMD processors, respectively; support for Windows Vista; and the Volume Shadow Service, which enables administrators to back up a group of virtual machines in one fell swoop by taking a snapshot of the physical server on which they're running.
Microsoft's desktop virtualization product, Virtual PC, is now free. More than 1 million copies have been downloaded so far, Neil said.