Richard Rhodes said: >I'd love to have a couple vtl's. When we've priced them out they come >out to be much more costly (several times) that of tape for our >environment. We keep lots of old/stale data around which drives seems >to drive the cost of the VTL way up. I was hoping possibly use a vtl >for only primary data with the new feature of TSM v5.4, but that's not >going to work out.
VTL cost (even after dedupe) will never compare with the cost of tape media alone, so tape will always be a cheaper medium if you take it out of the library. When I say that VTLs are close to the price of tape, I mean close to the price of a similarly-sized, fully-populated-with-media tape library. >I personal opinion is that VTL's are a stop-gap solution. I think >compression and de-dupe have much wider application within a normal >disk subsystem where it could apply to a much wider range of >situations. Pretty much everybody who is following the industry believes it will morph into the "intelligent disk target" industry. VTL will continue to be a personality they offer, but as other backup software products are better able to back up to filesystems (TSM does it just fine), more VTL vendors will offer a filesystem interface. Right now, the only one that does a filesystem interface and de-dupe is Data Domain. (Copan has a filesystem interface, but I don't think they're doing de-dupe through it yet. Any day now.) >This is the bit problem I see with Tape. It seems to me that the >latest generations of tape drives have rated speeds that almost >defy the any ability to supply them with data. I almost which >I could purchase a modern tape drive that actually was slower. Mmm... LTO-4: 120 MB/s native speed, 180 MB/s typical with compression. (I'm using 1.5:1 compression, which is what I see most often as an average actual compression ratio.) So... It wants 180 MB/s, and I've supposed to feed that with a 60-80 MB/s GbE connection. (The only saving grace of modern tape drives is that they have variable speeds. The LTO-4, for example, can go as slow as about 40 MB/s plus compression.) The problem is capacity. As vendors push capacity, they do so by pushing the bits closer together. As they do that, the drive gets faster.
