In a blog posting this morning, Microsoft general manager for virtualization strategy Mike Neil revealed his company will be pushing back some milestone dates for some of its key virtualization products. The first Windows Server virtualization product, code-named "Viridian" - specifically, the software that would enable a virtual Windows Server to run across up to 64 processors - will see its first public beta slip back to the second half of 2007; and service pack 1 of Virtual Server 2005 R2 (designed to run a virtual Windows Server on any Windows machine) will see its release date slip as much as three months, to Q2 2007.

Neil gave some hints that the reasons for the delay had to do with developing more new options for cross-processor scalability. "In an IT environment of ever-growing multi-core processor systems, Windows Server virtualization is being designed to scale across a much broader range of systems than the competition," Neil wrote. "We're designing Windows Server virtualization to scale up to 64 processors, which I'm proud to say is something no other vendor's product supports. We are also providing a much more dynamic VM environment with hot-add of processors, memory, disk and networking as well a greater scalability with more [symmetric multi-processor] support and memory."

The server virtualization tool was first announced at last year's WinHEC conference, and is still scheduled to be spotlighted at the next WinHEC in Los Angeles in three weeks' time.

Part of the confusion surrounding Viridian's release time has to do with the fact that it hinges upon that of Windows Server "Longhorn" (likely to be dubbed Windows Server 2007). At last year's WinHEC, Neil announced Viridian would be an integrated part of Longhorn; and in an interview published last June, he added that it would be available to customers within 180 days of Longhorn's release to manufacturing. In a statement to BetaNews this morning, a Microsoft spokesperson said that fact hasn't changed.

But if Viridian is being pushed back, is it because Longhorn is being pushed back as well? The spokesperson told us no. "There is no change in the schedule for Windows Server 'Longhorn,"' the spokesperson told BetaNews. "It remains on track for beta 3 in the [first half of] 2007, and RTM in the second half of 2007."

To recap, the formula stays the same, but the results change: Viridian will be released within a 180-day timeframe from Longhorn's RTM, which won't change...but Viridian's release could still be six months later. Or, interpreted another way, the schedule is corrected, since Longhorn was already slated for release in the second half of this year anyway.

Or interpreted a third way, there's no delay at all: "Windows Server virtualization remains on schedule," reads Neil's summary this morning.

SP1 of Virtual Server 2005 R2 will be pushed back one quarter, Neil says, to give Microsoft time to test implementations with new guest operating systems. One is Longhorn itself, which will likely be affected by changes in Viridian to account for more server scalability. Other guest operating systems supported will be SUSE Enterprise Linux 10 and Solaris 10.

In his post this morning, Microsoft's Neil said one of his team's goals for R2 SP1 is to enable a simultaneous 512-virtual machine implementation when hosted in 64-bit Windows.