When I describe data deduplication to users for the first time, the first two questions they ask always are, "Is this for real?," sometimes rephrased as "You're kidding me, right?," followed quickly with "What kind of deduplication ratios can I expect?"My standard answers are "Yes, it's for real" and "Nowhere in computing are the words 'your mileage may vary' more appropriate than when talking about data deduplication." Now Sepaton is guaranteeing that users will see a 40:1 reduction in the space their data takes up on a Sepaton VTL or Sepaton will give them more disk to make up the difference.

Since the folks at Sepaton aren't idiots, they're not going to be coughing up disk drives for every Tom, Dick, and Harry that can think up a set of data so random it can't be deduped. To qualify for more disk space, users have to make daily full backups of Exchange servers to a Sepaton FastStart package of VTL appliance, DeltaStor deduping software, and the first year's maintenance.

They'll also need to use Symantec's NetBackup since DeltaStor can only dedupe data from NetBackup format virtual tapes in the Sepaton library.

While the guarantee is a good way to make the point that deduping is for real, and generates some free publicity from bloggers like this intrepid reporter, I don't think Sepaton's going to have to pay off very often.

Truth is, 30 days of full Exchange server backups will contain a lot of duplicate data. After all, most users keep weeks, if not years, of e-mail messages in their mailboxes and all that old e-mail is in every backup. Add in the multiple messages with the same attachments, duplication across multiple information stores, and 40:1 doesn't look that difficult, especially for the large-scale Exchange environments with multiple servers and information stores that are Sepaton's target market.

Even if Sepaton has to shell out another disk shelf every once in a while, the $10,000 to $15,000 a JBOD (Just a Bunch of Disks) costs them isn't going to break Sepaton since it's selling the 20-TB (usable) FastStart package for $136,000.