Startup Virsto Inc. has turned heads among Hyper-V users. They say the technology helps overcome performance problems associated with dynamic disks in their server virtualization environments while streamlining storage capacity used by virtual machines (VMs). But larger shops say that the software won't move to production until it deepens its ties with Microsoft's System Center Virtual Machine Manager (SCVMM).
Hyper-V allows two virtual disk types: dynamic and fixed. Dynamic disks allow for thin provisioning but come with performance overhead. Microsoft's most recent estimates have dynamic disks performing at between 94% and 96% of comparable raw disk throughput. Fixed disks perform better (at 98% to 99% of raw performance rates) but allow less flexibility for capacity management. Virsto launched the first public beta of its Virsto One software in February and focuses on Hyper-V environments, though the company says support for Xen and VMware is also in its sights.
Virsto One is deployed within Hyper-V's parent partition. It intercepts I/O from guest machines and creates a sequential log file as a database would. As a result, writes and reads from disk are sequential in all cases. Further, when data is de-staged to disk, the log optimizes data layout and deduplicates redundant blocks of data to optimize storage capacity.
Virsto One also inserts pointers into its sequential log to create snapshots and clones and claims the ability to do a greater number of snapshots on this sequential stream of data with an order of magnitude faster performance than traditional snapshot mechanisms.
Hyper-V dynamic disks with fixed disk performance
Chris Routhe, an information technology analyst at Millard Kumber based in Omaha, Neb., manages IT resources for his company's 150 employees at two locations. He was recently tasked with replacing 15 aging physical servers on a minimal IT budget.
"We had to do something, and we didn't want to buy 15 brand-new servers," Routhe said.
About a month ago, the company migrated its 4-year-old physical servers to a single Hyper-V host with a directly attached Dell MD3000i disk array. Routhe weighed whether to use dynamic or fixed disks. Virtual disks would have saved storage space, but he couldn't be sure that using fixed disks wouldn't create too much contention for the 2 TB of physical storage space among the 15 machines. He needed to make the project work without having to purchase a bigger, more expensive storage array.
Enter Virsto, which Routhe used to reconfigure the MD3000i to raw disk format and optimize the layout of data on disk. "It effectively gave us dynamic disks with the same performance as fixed disks," Routhe said. He estimates the addition of Virsto allowed him to avoid having to purchase at least another terabyte of storage space.
Routhe said he has found Virsto's provisioning manager easy to work with and has been able to stand up new VMs in less than one minute with Virsto's snapshots and clones. "I don't really use SCVMM anymore," he said, except for physical-to-virtual conversions.
Wanted: better SCVMM integration
Larger Microsoft and Hyper-V shops, however, aren't as willing to part with SCVMM, and say Virsto needs to go beyond the integration with the Microsoft management tool it announced with version 1.2 in September.
Robert McShinsky, a senior systems engineer for Dartmouth Hitchcock Medical Center in Lebanon, N.H., manages 23 physical hosts and 400 virtual machines running on Hyper-V and was one of the earliest beta testers of Virsto's product. Currently, McShinsky said, the product remains in test at his facility while he awaits tighter integration hooks into SCVMM to unify the provisioning process between Microsoft's interface and Virsto's. "When you set up disks, you first have to create them through the Virsto console," McShinsky said. "We have a workflow in place to provision VMs through templates using SCVMM. … We're still waiting to get that provisioning process streamlined."
McShinsky said Virsto One 1.2 did satisfy a major item on his wish list by adding integration with Microsoft's System Center Data Protection Mananger (DPM). "That was one we were waiting for. We hit that part of the new release pretty hard trying to break it, but we didn't," he said. "It helps move [the product] further toward production."
But while he hopes for more polish on the management side, McShinsky says Virsto is the real deal when it comes to improving performance. Despite the fact that deduplicating data as Virsto does can result in contention for disk access among multiple virtual machines, McShinsky said he hasn't detected any "hot spots" on his Hewlett-Packard Co. EVA 8000 series 4 Gbps Fibre Channel disk arrays. "We've gotten up to 30 VMs on one host in tests," so far, McShinsky said.
He also said he finds the Virsto software, licensed at $1,250 per dual-core processor, "is very well priced for the potential storage savings, especially when a single Fibre Channel disk these days can be $1,000." But Virsto is in a tough market position as it tries to make a name for itself, he added. "They're producing a produt that helps the performance problems enterprise customers have, but the number of enterprise Hyper-V customers isn't very high yet."
Integration with SCVMM is due out before the end of the year, a company spokesperson said, with additional integration enhancements slated for the first half of 2011. "Close integration with the management tools of the server virtualization platform … is part of our product strategy," the company said in a statement. "This strategy … preserves the management semantics for tools like SCVMM with which [users] are already familiar."
Beth Pariseau is a senior news writer for SearchServerVirtualization.com. Write to her at email@example.com.