How green is your provisioning?

SVC's new thin-provisioning capabilities in your storage environment, could come with a green lining

Reaping the fat savings of thin provisioning may have gotten a little easier, as IBM last week announced new features for managing SVC (SAN Volume Controller). And depending on your strategy for implementing SVC's new thin-provisioning capabilities in your storage environment, the news could come with a green lining.

As the acronym suggests, SVC is all about block virtualization. SVC boxes sit between hosts and storage arrays, allowing admins to carve logical volumes and present them to application servers over FC connections. In addition to provisioning, SVC offers the ability to create snapshots and volume replicas both locally and remotely.

Although such features are common to most storage array controllers, SVC moves those capabilities up a notch in the storage hierarchy, in essence creating an abstraction layer that isolates application servers from changes to the storage system.

This approach allows administrators to manage disparate storage systems from the same SVC interface -- nice not only from an aesthetic perspective but also in terms of saving on training and administration costs. When I first stumbled into SVC in 2003, support was limited to a few IBM systems. Since then, Big Blue has built an impressive hardware-interoperability list that includes many competitors' arrays, making the abstraction layer even more powerful.

Think, for example, how much easier it is to replace an aging storage box when you can migrate its data on the fly to a new system without disrupting any application. Or how much you will save not having to buy a new array with sophisticated -- hence, more expensive -- management features. Buy a plain-vanilla "dumb" box, and SVC will deliver all the smarts you need -- now including thin provisioning.

To understand thin provisioning, think of a contract in which your storage system commits a specific-size volume to the application server to be delivered gradually and only when requested. In essence, non-thin provisioning is similar to having a supplier dump a year's worth of bottled water at your front door. With thin provisioning, the supplier waits for you to make a request before delivering only the number of bottles you ask for.

Thin provisioning may not be appropriate for every application, but when it is, it translates into significantly higher storage utilization. This is because the number of blocks allocated to a host but not actually used is reduced considerably. In a large installation, that could mean buying fewer storage boxes or at least pushing that purchase off until later.

With that in mind, I wasn't surprised to read IBM's green spin in the SVC press release: "Virtualization is one of the five pillars of IBM's Project Big Green offerings."

Truth be told, in my follow-up briefing, IBM said thin provisioning had been added because customers had been requesting the feature. And though it is true that you could take advantage of a denser allocation of storage to reduce the number of boxes, I suspect the customers' desires for thin provisioning may not have rested entirely on going green. After all, performance demand suggests spreading your data over as large a number of spindles as possible.

Regardless of where customers stand, there is a silver lining for those who have been waiting for thin provisioning: They can get thin provisioning for free by downloading the new version of SVC, which should become available at the end of the month.

When I have a chance to take the new features for a test spin, I will be in a better position to say whether they will prove worthwhile. If the new features pass muster, customers will suddenly be able to extend thin provisioning to all their arrays, regardless of brand or how old they are.

Will this make customers' setup greener? Perhaps. It all depends on how they intend to take advantage of thin provisioning.

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