EqualLogic: Thin Is In

EqualLogic has added thin provisioning to the roster of features in the latest version of software for its PS Series iSCSI SANs.

"You can now logically overprovision LUNs without physically doing so," says director of product management Eric Schott.

Thin provisioning is the technique whereby physical disk capacity is used only as needed by multiple applications, obviating the need to add storage in advance of fully utilizing it. (See 3PAR Debuts 'Thin Provisioning' and A Data Reduction Dossier.)

Up to now, thin provisioning has applied mostly to expensive Fibre Channel arrays. In the IP SAN world, LeftHand Networks' SAN/iQ software uses a similar method of drawing on storage only as needed. Indeed, LeftHand claims thin provisioning on snapshots as well as volumes of storage. Intransa says it's working on thin provisioning, among other features, with no date for delivery. Now, EqualLogic's entered the fray.

EqualLogic's making thin provisioning a standard feature of its operating system, so that customers can use it or not as they choose. They can convert storage volumes to or from thin provisioning, avoiding having to make any firm decisions about it. The new release will ship in Q2 and be free to all supported customers.Schott acknowledges that thin provisioning may take a bit of getting used to, as administrators plan ahead on how to set parameters to extend storage volumes. Every application will differ. The key is to understand the growth rate of an application and be able to anticipate when thin provisioning will have to give way to actually supplying more storage.

There's some "guesstimating" involved, Schott says. "If you're talking to a database administrator, they know the database size; they have a feeling for it. It's local knowledge coming from familiarity with the operating environment. It's somewhat of an estimate."

Guesswork aside, at least one early adopter says there's nothing complicated about EqualLogic's new feature. "In my opinion, it's going to solve some problems for administrators," says Alan J. Hunt, manager of operations at Michigan-based law firm Dickinson-Wright PLLC. For example, he says EqualLogic's new thin provisioning helps with booting from SAN for over 60 diskless servers in his network.

"I want to keep the boot volume on the standard image small," he says. Thin provisioning lets him overcome the inability to extend a booted volume in Windows. "Now, I have to extend storage behind the scenes for the boot volume, while the server's down. With thin provisioning, I give the volume a larger value so I don't have to do that."

EqualLogic's also added some other features to its software. Role-based management, for one, gives differing privilege levels to different administrators. One could have access to a pool for storage for only their department, for instance. Similarly, a service provider could extend access to customer for disaster recovery without affecting other customers.Mary Jander, Site Editor, Byte and Switch