A storage virtualisation start-up called Virsto Software has developed a Microsoft Hyper-V add-on that speeds up access to data in virtualised data centres.

Virsto was founded in 2007 by former executives of Sun and Veritas Software who want to eliminate the I/O bottlenecks caused when virtual servers try to access storage systems. Virsto's first product, Virsto One, focuses on Microsoft's Hyper-V rather than VMware because VMware already has some functionality improving storage performance, says Virsto CEO Mark Davis.

"Microsoft needs more help" because its virtualisation technology is newer than VMware's, Davis says.

When talking to customers Davis says he hears a common complaint: "People say 'we love virtualisation, but storage is sort of busted.' The way storage works on physical machines doesn't translate to the virtual world."

With virtualisation, each physical server is packed with virtual machines, with each one taking up large amounts of storage and acting as if it owns the hardware, even though it is sharing resources with other VMs, Davis says.

Virsto claims it can reduce VM disk consumption by as much as 90%. Virsto's software, generally available starting this week, installs into the hypervisor and manages its interaction with any type of storage, Davis says. For example, Virsto ensures that storage systems perform sequential reads and writes, rather than random, reducing the amount of time needed by the disk head to do its job.

Virsto also reduces storage sprawl by preventing files from being needlessly duplicated. If you have 100 copies of Windows, not every piece of the operating system needs to be stored 100 times. Virsto's process of preventing this is similar to de-duplication but "we call it no-dupe – we don't make the copies in the first place," Davis says.

Thin provisioning, snapshots, clones and live migration are other features of the Virsto software.

Davis previously held positions at Sun and StorageTek and most recently was CEO of storage management vendor CreekPath Systems, which was acquired by Opsware in 2006.

Hyper-V is obviously behind VMware in terms of adoption, but "we're not having a hard time finding customers who are excited about Hyper-V," Davis says. "They're trying to find the best way to put Hyper-V into production."

Crutchfield, a consumer electronics retailer in Charlottesville, Va., has been testing Virsto and plans to put it into production soon. Roger Johnson, technical lead for Crutchfield's enterprise systems group, says he was sceptical about Virsto's claims at first but his tests have produced a 33% performance improvement in I/O throughput. Crutchfield is running 225 virtual machines on 11 servers.

"I was concerned about how it would do for large numbers of virtual machines for large periods of time," he says, but the results were "pretty impressive."

Virsto is operating with $8.25 million in funding from August Capital and Canaan Partners.

Virsto One can be evaluated for free for 30 days. Perpetual licences cost $1,250 for one or two sockets, $2,500 for three or four sockets, and $5,000 for unlimited sockets.