I just saw an interesting article by Chris Mellor over at The Register. Chris was speculating on why we haven't seen any deduplicated backup on tape. Because, hey, if I can squeeze 20 times as much data on a disk using deduplication technology, doing so on tape has to be a good thing, right?
And it would allow tape vendors to show that the technology has some relevance beyond long term archiving.
Chris has a lot of good explanations as to why we don't have dedup on tape yet—except from CommVault and EMC. But he misses the biggest reason of all: it might be really good for backup, but it is horrible beyond belief when it comes to restore. And as myself, David Chapa, and every other backup specialist will tell you, it is all about restore.
Why is it so terrible? Seek time.