At 03:40 PM 8/29/2007, Kelly Lipp wrote:
Help me get it because aside from the typical "I gotta have it because the trade rags tell me I gotta have it", I don't get it!
Kelly, I think you are correct in that TSM already gives you some of the benefits that a more traditional backup product would get by using a dedup VTL. But TSM only does it at the file level. I.e., if a file doesn't change, TSM won't back it up again, whereas other backup products might. But a dedup VTL will go further, in that it will dedup more information. For example, common files that exist across a bunch of clients (think about emails, attachments, Windows System Objects), or also things like Oracle database backups. There is still a benefit to using a dedup VTL in a TSM environment, but not nearly as great as in a traditional backup environment (father/son/grandson). Since you will likely pay some sort of premium for a dedup VTL, the question is: is the premium worth it? Or would you be better off buying a bunch of cheaper storage (tape or even SATA disk) and storing those extra copies? The answer, of course, is "it depends". But I think dedup VTLs will be a harder sell in a TSM environment than in other environments. As I've researched this, I'm thinking more about buying a smaller dedup VTL as an adjunct to our other back-end storage, which would allow us to target certain types of data that we know will dedup well, such as Windows System Objects, Exchange server backups, Oracle backups, etc. One problem with this, is that the best way to do this is via TSM management classes, but they are overloaded with other things like retention, versions, etc. It might be nice to see TSM introduce some new capabilities to help support a dedup VTL, or perhaps do some of what Curtis calls source-deduping. I know they've been thinking about something along these lines for awhile. One other point about dedup VTLs: some do their deduping in-band whereas others do them out-of-band. The in-band ones will avoid storing duplicate data, but can be more performance limited. This is only an issue if you need to move more data than they can handle. The out-of-band ones will store the data, then dedup it afterwards. At least one of these that I know of (Sepaton) can scale their performance by adding engines. I believe that one vendor recently now supports either way of doing this. ..Paul -- Paul Zarnowski Ph: 607-255-4757 Manager, Storage Services Fx: 607-255-8521 719 Rhodes Hall, Ithaca, NY 14853-3801 Em: [EMAIL PROTECTED]
