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Storage virtualization for better capacity management

Server virtualization has led to cost savings through server consolidation, and desktop virtualization promises efficiency gains in terms of desktop management; but storage virtualization is a missing link CIOs can use to maintain efficiencies and savings across the virtual infrastructure.

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At its basic premise, storage virtualization allows you to pool storage for better capacity allocation and management.

"Data is now in a logical pool, so the IT staff only gives out the amount of storage that is needed, versus overallocating storage, which is what usually happens when storage isn't virtualized," said Mike Piltoff, senior vice president with IT service provider Champion Computer Solutions LLC, of Boca Raton, Fla.

Efficiency gains can also be significant: Nonvirtualized storage arrays typically have a utilization rate of about 35%, while virtualized storage arrays give you a utilization rate of about 80%, Piltoff said.

Because storage is being pooled more efficiently, CIOs have a better understanding of how many new storage arrays and devices need to be purchased as their virtual infrastructure grows -- as opposed to "sticking a finger in the air and judging the wind to make the best guess estimate," said Chris Wolf, analyst with Midvale, Utah-based Burton Group.

Storage virtualization and thin provisioning

Pooling storage through thin provisioning is not a new concept, but by coupling thin provisioning with storage virtualization, IT staff can leverage thin provisioning across different arrays from different vendors. That gives the CIO a better view of overall storage capacity and the ability to use the capacity already in place more effectively.

The downsides to using one vendor's storage virtualization product to manage other vendors' products are the miscommunication that's possible when it comes to making a support call, and the issue of vendor control."He who controls the virtualization engine ends up controlling a lot of components that could lock you into that vendor," said Keith Norbie, vice president of Nexus Information Systems, a systems integrator based in Minnetonka, Minn.

Among storage virtualization's many variations, array-based is the most popular because many storage array vendors include such virtualization features as thin provisioning and replication, which make storage less expensive and easier to manage, experts said. Whether an organization chooses array-based, appliance-based, network-based or another type of storage, many storage virtualization products are designed for data mobility to avoid vendor lock-in. "Storage virtualization does allow you to move capacity off of EMC and onto Hitachi, or off IBM onto HP and so on," Norbie said.

Some storage virtualization vendors have thin provisioning with snapshot capabilities that let IT departments store a pristine disk image for quick server and desktop restoration, or to quickly update virtual servers or virtual desktops at once.

"I can leverage snapshotting features in the storage network to spin up hundreds of desktops almost instantaneously," Burton Group's Wolf said. "Features like thin provisioning and deduplication are essential because the ROI case for virtual desktops is pretty sketchy -- such as the potential storage costs."

For instance, with a traditional desktop, the cost of a local disk is around $80 per terabyte, but in a virtual desktop environment using a storage area network, one gigabyte will cost about $10 because a SAN has other components, such as a high-end disk array and cables, experts estimate.

On the other hand, thin provisioning can reduce the number of storage arrays needed to support a virtual infrastructure. "Thin provisioning, depending on the [cost of the] storage arrays used on the back end for the virtual environment, results in tens of thousands in savings," Wolf said. It's not unheard of to see ROI within a year of buying a storage virtualization device, simply because it eliminates the need to buy new back-end arrays, he said.

Storage virtualization can also help IT departments deal with the strains that desktop virtualization can put on network capacity, such as user-boot storms and the redirection of My Documents onto the file system. "If you take a [Windows] desktop and virtualize it, you're taking the My Docs folders and redirecting them into a [Common Internet File System] directory and you're also taking all the data on the hard drives and redirecting them virtually into that file system. File virtualization and deduplication will give you better efficiency on overall file consumption," Nexus's Norbie said.

The virtualization strategy gap

The biggest gap with virtualization isn't the individual components -- storage, server, desktop and network virtualization, for example -- it's lack of strategy.

Features like thin provisioning and deduplication are essential because the ROI case for virtual desktops is pretty sketchy. 

Chris Wolf, analyst, Burton Group

"People have integrated VMware with other virtualization components and they have server-based virtualization in place, but they do not have a checklist of what needs to be looked at across the network; and with virtualization everything dovetails together," Champion Computer's Piltoff said.

Piltoff sees customers using one vendor for network virtualization, another for server virtualization and another for storage virtualization: "It's like having all these countries come in speaking a different language," he said. "My advice to CIOs is, if a vendor comes to you talking about virtualization in piece-parts instead of a holistic approach, choose a different vendor."

In essence, virtualization creates more data in the form of image replicas or snapshots. Instead of introducing virtualization management tools that address added storage and network capacity needs, many organizations throw money at bottlenecks and push the bottlenecks around from desktops to servers to storage, Piltoff said.

CIOs also need to keep in mind that switching storage virtualization vendors can be just as painful as migrating data from one storage array vendor to another. "Doing any type of migration will consume a tremendous amount of resources on the storage network; those issues persist with storage virtualization," Burton Group's Wolf said. "And if you use features such as thin provisioning on a storage virtualization device, you're going to have to undo those features as part of the data move."

Let us know what you think about the story; email Christina Torode, News Director.

This was first published in February 2010

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