Sanbolic has adapted its clustered file system to support Microsoft's upcoming hypervisor, allowing IT shops to move a virtual machine from one physical server to another without affecting users.

While server virtualization market leader VMware enables the seamless movement of virtual machines with a product called VMotion, Microsoft's Windows Server 2008 Hyper-V, currently in beta, lacks such technology, according to Bill Stevenson, Sanbolic's executive chairman.

"Clustered file systems are a complex technology and Microsoft currently does not have technology in-house that enables them to do that," Stevenson says.

With Sanbolic supporting Hyper-V, a file that contains a virtual machine image can be stored in a shared LUN storage unit, and be accessed by multiple physical servers, he says. Any virtual machine can then run on any physical host.

"To move a virtual machine from one physical server to another physical server, there's no need to change anything in the storage connection because both machines see that image," he says. "You stop it on one machine and start it on another machine."

PolyServe, a network-attached storage vendor acquired by HP last year, makes a similar clustered file system product

The new Sanbolic Melio 2008 clustered file system is being announced Monday, one day before the VMworld Europe 2008 Conference in Cannes, France.

Microsoft, which is attending VMworld to give demos of Hyper-V, acknowledged Sanbolic's support of its hypervisor. "We are very pleased that Sanbolic's clustered file systems will be available to our customers as they deploy virtualized applications on Windows Server 2008 Hyper-V," said Zane Adam, senior director of virtualization strategy at Microsoft, in a press release.

But Sanbolic technology won't actually be embedded in Hyper-V, leaving the door open for Microsoft to build its own technology or pursue other partnerships.

"They have not bundled or OEM'd the product at this point. ... That could change over the next six months," Stevenson says. "We expect to be publishing joint reference architectures."

Without a clustered file system like Sanbolic's, moving virtual servers created by Hyper-V to a different physical machine requires some extra legwork, such as copying a virtual machine image to storage that can be accessed by the second physical server.

That can get complicated when you have hundreds of virtual machines, Stevenson says.

While that extra work is eliminated with Sanbolic, moving a virtual machine would still require about 5 to 10 seconds of application downtime, he says.

Sanbolic's technology costs US$5,000 for each server connected to shared storage.