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Hyper-V add-on promises cheaper storage

Beta testers have taken a shine to Virsto One, which they say improves I/O performance and snapshot capabilities in Hyper-V shops.

New storage virtualization software from Virsto Software dramatically improves storage performance in Microsoft Hyper-V virtual environments and, by extension, will help these IT shops reduce storage costs, beta testers say.

Announced on Tuesday, Virsto One installs into Microsoft Windows Server 2008 R2 Hyper-V as a filter driver, providing high-performance, thin-provisioned snapshots and clones and increasing I/O performance.

"If I hadn't seen it with my own eyes I wouldn't have believed it, said Roger Johnson, the technical lead at Crutchfield Corp., an electronics retailer in Charlottesville, Va., which has been testing Virsto's software since October.

Specifically, Johnson said he had encountered 30% better I/O performance from his virtual machines running on Virsto vDisks as compared with native Microsoft VHDs. Johnson provisions three virtual machines per disk spindle. But with Virsto, he now can drive that ratio higher without an associated drop in performance.

The I/O blender effect

One of the main problems Virsto attempts to solve is the "I/O blender effect" common to all server virtualization platforms, said Ryan Jones, a virtualization product manager at MaximumASP LLC, a Windows hosting provider and another Virsto beta tester.

If I hadn't seen it with my own eyes I wouldn't have believed it.
Roger Johnson

The I/O blender effect occurs when multiple virtual machines (VMs) all send their I/O streams to a hypervisor for processing. Under heavy loads, VM I/O -- which might otherwise have been relatively sequential -- becomes random, increasing the read/write activity on disk heads and increasing latency. Virsto One intercepts incoming I/O and reorders it so that it is smoother, said Mark Davis, Virsto's CEO.

This problem is not unique to Hyper-V. "Pretty much all the vendors struggle with the same set of issues. As soon as you start to see 25:1 or 30:1 consolidation ratios, you're going to see some I/O contention," Jones said -- that is, "unless you have huge disk arrays or you are totally underutilized."

As a hosting provider, Jones said Virsto's software will help MaximumASP's bottom line. "What we liked about Virsto was that we get premium features of high-end storage arrays, and better performance out of our commodity storage arrays. We expect to get more revenue per gig[abyte] when using Virsto," he said.

Snapshots and clones

Virsto One also provides thin-provisioned, high-performance snapshots and clones. Crutchfield's Johnson said that without Virsto, developers lose valuable time when they have to clone of a VM for testing purposes.

Without Virsto, "the provisioning process is basically a file-copy process. Depending on the speed of the disk, you could be waiting 15 minutes for the clone to be ready," Johnson said. But with Virsto One in place, creating a clone "is never more than a three-second wait," he said.

Further, Virsto's snapshots are much more space efficient and thus consume less storage than with Hyper-V on its own.

No VMware, no VMM integration -- yet

We're looking forward to integration with [Virtual Machine Manager].

On the whole, Virsto beta testers like the offering but noted that the company can make Virsto One a more complete product.

"We're looking forward to integration with Virtual Machine Manager (VMM)," said Crutchfield's Johnson. As it stands, provisioning storage with Virsto is done through the standalone Hyper-V Manager. By working directly with Microsoft's VMM, Crutchfield developers can now provision Virsto vDisks themselves, through a self-service portal.

MaximumASP's Jones said he looks forward to seeing deduplication across cloned disks.

"We have hundreds of VMs based on four base images. There's very little difference between them at startup, but as time goes on, changes get applied to them like the latest [Internet Explorer] patch," he said. Applying deduplication to changes would greatly reduce disk consumption, he said.

Other observers said they hoped the company would port the product to VMware. Tom Becchetti, a Unix and storage administrator at a large manufacturing company, is a member of Virsto's advisory board and said that he would use Virsto's offering in his VMware environment if it were available.

"We'd use it for the I/O performance. As you start scaling up these farms, our performance starts to dwindle," Becchetti said. VMware VMs in his environment have 12-to-50-millisecond response times compared with just 2-to-5-milisecond response times for dedicated servers.

Virsto CEO Mark Davis said the software was architected to be hypervisor-agnostic, but that it was premature to announce a version for VMware or for any other hypervisor. "We're on the birthing table," Davis said. "This is not the time to ask us if we want to have another baby."

More on storage for Hyper-V virtualization environments

New Hyper-V R2 storage features offer hot-add and remove capabilities

Optimizing virtual hard disk performance in Hyper-V

With Hyper-V's clustering and storage, who needs HA?

Let us know what you think about the story; email Alex Barrett, News Director at, or follow @aebarrett on twitter.

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