Microsoft has released the second beta of Virtual Server 2005 R2 Service Pack1, adding promised support for AMD's virtualisation technology, along with improved backup and administrative functionality.

Support for AMD's technology, which the chip company recently introduced in its Opteron processor, matches support for VT, Intel's rival technology, which Microsoft included in the software's first beta release.

The core benefits are a performance boost for non-Windows guest OSes, and strengthened isolation to prevent corruption of one virtual machine from affecting others on the same system, according to Microsoft.

Microsoft reckons the software also includes a Volume Shadow Service, which improves server backup processes. 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 while backing them up.

The latest beta 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.

Virtual Server 2005's virtualisation capabilities will be built into the next version of Windows Server OS, code-named Longhorn, slated to be available sometime next year, according to Redmond. The company also said Vista would be added as a supported guest operating system when Virtual Server 2005 R2 SP1 ships.

In April of this year, Microsoft stripped the US$199 price tag off Virtual Server and began offering it as a free download to its Windows users. At the same time, Microsoft also announced support for Linux as a guest operating system.

Virtual Server 2005 R2 SP1 is scheduled to ship before the end of March 2007. It can be downloaded free here.