A few more points: - It's true that hardware compression is faster than software compression, and off-loads the server. Hardware compression often is an extra-cost item. This can also be true of encryption, if done in hardware. The question is, where do you want to do your encryption? At the storage device, on the network, or in the client? Depends on your requirements.
- Deduplication is going to take processing time wherever it's done. Be it by TSM on the TSM server, or by the VTL either in-band or out-of-band. Just because it's done out-of-band doesn't mean that you don't have to worry about performance. You still only have 24 hours in a day to get everything done that you need to get done. - TSM is in the best position (IMHO) to do deduplication, because it knows most about the data. To illustrate this, consider the following: Even with a VTL, you will still be doing TSM Tape Reclamation. With a VTL, the input tape will have to be "rehydrated" as it is read, and the output tape will have to be "re-dehydrated" as (or after) it is written. TSM, on the other hand, could know that the data on the input tape has already been dehydrated and therefore doesn't have to be re-dehydrated on the output tape. It knows what the data is. (n.b., I don't know how TSM will do this - this is hypothetical - time will tell). There can be other examples of this also, especially thinking forward. VTLs are more limited in what they can do. Their advantage is that they can be dropped in to replace a physical tape library transparently. - Given that you're going to have to pay for the extra processing one way or the other (either by the higher cost of a deduping VTL or by bigger processors on your TSM server), I'd rather invest my money where the most intelligence can be - in the TSM server. Compare the cost of inexpensive disk to the cost of the VTL solutions you are considering. Using a highly-featured disk subsystem for serial-access disk may not be the best way to spend your money for serial-access-disk. Look at simple SATA arrays. My last point - there are a few VTLs that have replicating dedup today, with more "on the cusp". If you need something today, look at what is available today. If you don't need something until later, re-evaluate the marketplace later - it's very dynamic right now. ..Paul -- Paul Zarnowski Ph: 607-255-4757 Manager, Storage Services Fx: 607-255-8521 719 Rhodes Hall, Ithaca, NY 14853-3801 Em: [EMAIL PROTECTED]
