Virtual Headaches

Storage virtualization is hot, and for good reason. But its benefits bring added layers of complexity.

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Headache 5: Getting the Right Gear

Babu Kudaravalli, senior director of business technology operations at National Medical Health Card Systems Inc., gives this definition of storage virtualization: "The ability to take storage and present it to any host, of any size, from any storage vendor." He's pursuing those goals with three tiers of storage, each supported by a different HP StorageWorks product. The technology used in each tier is chosen for the mix of cost, performance and availability it offers.

Kudaravalli uses high-end HP XP24000 disk arrays for the most demanding and mission-critical applications, lower-cost Enterprise Virtual Array 8000s for second-tier applications, and Modular Smart Array 1500s for archiving, test systems and the like. His five SANs hold 70TB of data, of which about 35TB in the EVA and MSA tiers is virtualized, he says.

Kudaravalli says there are several things to be careful about when buying storage virtualization products. First, be aware that vendors typically certify their products to work with the latest versions of other vendors' products. If you don't have those exact versions, your interfaces might not work. He says this is a good reason to think about replacing your old gear when you go to a heterogeneous storage environment -- or at least to keep current on the latest releases.

Second, Kudaravalli says that although virtualization should ultimately simplify storage management, setting up a virtual system is complex. Careful planning and an understanding of the limitations of products is crucial.

A few years ago, vendors had very different definitions and standards for virtualization, says Kudaravalli. "But now they seem to be coming together," he says. "They are trying to offer similar features and capabilities, but it is not completely mature."

How to cope: Although storage virtualization is often undertaken to better utilize existing resources, it may have a perverse impact, says Rick Villars, a storage analyst at IDC. "The whole point of virtualization is to make it easier to provision or move a resource, to create a new volume or another snapshot, or to migrate data from one system to another," he says. "But when you make something easy to do, people are induced to do it more often."

According to Villars, volumes, snapshots, data sets and even applications can needlessly proliferate. "You can go from being more efficient to more wasteful. It's just what can happen with virtual server sprawl." Preventing that is a matter of policies, procedures and good business practices, not technology, he says.

Users agree that there are many technical details to master when pursuing storage virtualization. But Navarro suggests starting with a basic question: Why am I doing this? "Virtualization is a hot word, a big thing. But is it really necessary? There are benefits, but ask yourself if you are doing it for the right reasons, or just because you want to be on the cutting edge. It's very easy to get swept up in these groupthink movements."

This version of the story originally appeared in Computerworld's print edition.

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Next: Five questions to ask before launching a storage virtualization project.

Copyright © 2008 IDG Communications, Inc.

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