Just a couple of weeks after releasing Windows Server 2008 RC0 to TAP customers, Microsoft is ready to open the new build to general public. Since it includes a technical preview of upcoming Windows Server Virtualization (codename Viridian), this is the first time the new Microsoft hypervisor reaches such a wide audience.
Viridian adopts is a true bare-metal Virtual Machine Monitor (VMM) compared with existing Virtual Server 2005 R2 SP1, using a 64bit microkernel not derived from existing Windows kernel which takes only 1 MB space on disk (but requires Intel VT or AMD-V extensions enabled on phyical CPU) and finally supporting 64bit virtual machines (check the architecture here).
Current technical preview is capped to 4 vCPUs per VM if you have Windows Server 2008 as guest OS, while it’s capped to 1 vCPU per VM if you have Windows Server 2003 as guest OS. Other temporary limitations imply only 64GB of addressable RAM , only one virtual SCSI device, and only one virtual NIC (final version is expected to feature 12 per VM).
Last but not least this technical preview features a complete Windows Server installation in its parent partition, contrary to what Microsoft initially stated (Windows Server 2008 Server Core edition as the only allowed OS in parent partition).
It’s also worth to remember that this build is not comparable with a standard beta, and despite its early availability Microsoft didn’t change its scheduling: final version of Viridian will be available 180 days after Windows Server 2008 RTM (set for February 28, 2008).
Update: Despite informations provided, it seems Viridian can create Windows Server 2003 virtual machines with 8 vCPUs.