Microsoft has put Virtual Server 2004 out to 15,000 testers for beta.

The upcoming server, built on the virtual machine technology acquired from Connectix in January 2003, now contains support for a range of SCSI drives and two-node clustering that will allow failover from one virtual machine to another, as well as offer greater security.

With x86 emulation built in to Virtual Server 2004, it will also support a range of different Intel-compatible operating systems - including Linux.

"We have also improved and enhanced what we think is one of our biggest competitive differentiators, which is our COM API," said Eric Berg, a product manager in Microsoft's Windows Server group. "We have a very rich, programmatic interface into Virtual Server. This will make it easier for administrators to script and automate a lot of the different capabilities."

Microsoft has also spent time integrating the server with its management tools so virtual and physical servers exist side by side. "Rather than taking the approach of having a separate tool manage virtual machines, we wanted to have tools that could manage Virtual Server and associated physical servers in harmony. That was clear from the user feedback we got," Berg said.

The beta program has two tiers. The first, and smaller of the two, is a joint development program of 30 users. The second, a much broader offering "news group level" support to about 15,000 developers.

Microsoft is aiming the server at those looking to do software testing and development (who can simulate a distributed server by carving up a server into virtual machines), and corporate users that want to consolidate their business apps under Windows Server 2003.

"This is a good product for those with legacy apps running on a Windows 2000 or NT 4.0 and to put them all up under the latest version of our server operating system," Berg said. "It is also good for those looking to consolidate servers within a disaster recovery environment. So instead of having an equal number of servers in both disaster recovery and production, they could use Virtual Machine to reduce their number of physical servers."

Virtual Server 2004 should be available by the middle of the year.