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Virtualization: Tales from the trenches

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Virtualization Tips
Virtualization products can be a boon to your storage environment, but they come with their own level of added complexity. To make your transition to virtual storage easier, you should do the following:

Check operating system compatibility. Many virtualization products require agents to be installed on your servers. Check to make sure your current operating system levels are supported by the agent software.

Check SAN and storage hardware compatibility. Some virtualization products support a wide range of storage and SAN

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hardware, but have only been validated in specific configurations. Verify that your SAN configuration and storage hardware are currently supported or can be brought into compliance with supported configurations.

Check your virtual storage configuration. Virtualization products may have limitations or guidelines on how much storage is supported per virtualization node. Make sure you operate within the performance and capacity envelope the vendor recommends.

Change your way of thinking. You may be used to defining LUNs and assigning them to specific RAID groups, but with virtualization you won't have to anymore. Although these products will let you continue to do that, they work better if they decide which back-end RAID groups to assign to which virtualized LUNs.

Virtualizing HP and HDS storage
After experiencing problems with an in-band virtualization product, Todd Wyman, Unix storage administrator at a Midwest manufacturer, says his company opted for StoreAge's SVM, an out-of-band, host-based product. The company has approximately 45TB behind SVM, with both HDS Thunder and Hewlett-Packard Co.'s Modular Smart Array (MSA) storage, a Brocade Communications Systems Inc. SAN infrastructure, and servers running HP-UX and Windows.

The StoreAge SVM was installed in January 2005 and Wyman says it took his firm approximately a year to migrate fully to the new environment, which was achieved without buying additional storage. Wyman's company carved up a bit of its current storage to virtualize it, migrated other storage to that and then virtualized the newly freed storage. In this fashion, they virtualized their whole complex of existing storage over time.

Wyman says the company is using StoreAge's multiMirror (remote replication) in asynch mode for its disaster recovery site. It's also using point-in-time copy mirroring at the remote site and has added point-in-time copy to its other backup scripts.

Wyman encountered some issues during installation when SVM's host software agents wouldn't run on some older HP-UX systems to support SAN boot, but StoreAge remedied the problem. Some bleeding-edge Windows servers also needed to be certified with StoreAge SVM, which was a Windows certification issue not a StoreAge shortcoming. "It's not if there will be issues, but when," says Wyman. "And when they do occur, it's how well they respond that matters." With open systems, there's an almost infinite number of combinations of OS levels, host bus adapters, SAN hardware and storage--and, often, not all of it can be validated in advance.

Wyman has only praise for the level of service provided by StoreAge and the easier management SVM affords. "Single pane-of-glass management is a boon for anyone," says Wyman, who also likes the performance he's seen so far. He says performance has improved because he's now striping his virtualized LUNs across many more disk spindles.

This was first published in August 2006

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