In his Storage Decisions conference presentation titled "Attack of the Killer Capacity," Mike Matchett discussed different methods of capacity optimization and their benefits, including storage thin provisioning. Matchett, a senior analyst at the Taneja Group, reminded storage managers to make sure their thin provisioning features stay thin.
"Make sure that when you're looking at thin provisioning, that when you take a snapshot it stays thin and doesn't fully hydrate just to take the snap. Same with a clone. If I take that snapshot and turn it into a clone that clone should stay thin, to be optimal in capacity," Matchett warned. "There's no reason to hydrate that. If I replicate that snapshot or that clone or that original thin image it should stay thin."
One risk associated with storage thin provisioning is oversubscription. Oversubscription is actually one of the ways thin provisioning can help with storage efficiency -- by setting aside a large amount of storage, but only using a small amount at a time. Yes, this allows for automation and less time spent on allocating storage. But, those who use oversubscription run the risk of running out of space quicker than they expect.
"There are certain applications that might actually not use that much data but over time make that volume thicken out and then drop back down," explained Matchett. "So it doesn't look like the total space used has gone up much but the thin percentage has gone up considerably."
The bottom line, said Matchett, is that thin provisioning is so automatic that many people believe it shouldn't have a performance impact in today's modern storage arrays -- but it can indeed.