Microsoft has released another test version of an update to its virtualization software, which will be built into the next version of the Windows Server OS.

On Thursday Microsoft released Beta 2 of Virtual Server 2005 Release 2 Service Pack 1 (R2 SP1), an update that will add new functionality to the existing version of Virtual Server 2005 once it is generally available. The software, which should be in full release by the first calendar quarter of 2007, can be downloaded for free from http://www.microsoft.com/windowsserversystem/virtualserver/default.mspx

New features included in Beta 2 of the software are support for Advanced Micro Devices's virtualization technology, as well as new integration with Microsoft Active Directory, Microsoft said.

The software also includes what is called a Volume Shadow Service, which improves the server backup process, according to Microsoft. Instead of scheduling downtime to back up each virtual machine individually, the software will take snapshots of physical machines. Those physical machines will in turn take snapshots of all the virtual machines on the physical host. This enables server administrators to keep virtual machines up and running even while backing them up.

Beta 2 of Virtual Server R2 SP1 also includes new offline virtual hard disk (VHD) mounting, which enables customers to view and manipulate files in a VHD without having to start a virtual machine. This enables administrators to easily deploy scripts and perform virus scans across VHDs without having to start each virtual machine, Microsoft said.

Microsoft introduced Virtual Server in October 2004. The product enables virtualization of Windows so multiple instances can run simultaneously on one server as if they were running on multiple servers.

Microsoft has said virtualization capabilities that are available in its Virtual Server 2005 product will be built into the next version of Windows Server OS, code-named Longhorn, which is slated to be available sometime next year.