I believe that the restore performance for small files is impacted by how spread out they are on tape (the same tape, not different tapes). If all of the files you are restoring are contiguous, I believe that tape can perform much faster. The problem we run into is that there are gaps between the files. Caused either by expired files, or other nodes sharing the same tape (even with collocation, if you have multiple nodes per tape). Thus, when doing performance testing on tape, it is important to understand the test data that you are restoring (i.e., whether the files are contiguous on tape or not). We have found this makes a noticeable difference.
Jon, when you state that "the more clients you add, the slower each backup stream becomes", are you talking about TSM clients? If so, are you talking about simultaneous backup streams, or just the fact that multiple clients are registered on the TSM server? I'm trying to understand what the cause of the performance degradation is. We have also been considering data reduction type devices to add to our TSM environment. I am curious whether you are using client compression or client encryption, and to what degree that interferes with the reduction. FYI, Sepaton recently announced a data reduction capability on their vTape product. I don't know too much about it, but I think it does after-the-fact reduction by scanning files already stored. ..Paul At 10:49 AM 5/16/2006, Jon Evans wrote:
I have recently tested a DD460 for exactly the same reason. The results showed that compression was good (upto 20x) but throughput was not so good. The more clients you add, the slower each backup stream becomes. Off course, much depends on your infrastructure, and these results were based on a windows filesystem, running across a gb network. Unfortunately, with millions of small files it is very difficult to improve performance significantly. Personally, I could not improve backup or restore performance over an LTO2 or LTO3 tape drive, and the tape drives still work out cheaper.. so I decided against it at this time.. Regards Jon Evans -----Original Message----- From: ADSM: Dist Stor Manager [mailto:[EMAIL PROTECTED] On Behalf Of Christoph Pilgram Sent: 16 May 2006 14:43 To: [email protected] Subject: Disk-to-Disk Backup Hi all, Because we have problems to hold our service level agreements with the customers for restoring big file-servers (10 Mio files, 1TB disk-space in one filesystem), we are thinking about storing the backups not anymore on tape but on disk. Does anybody has experience with that kind of storage-pool for about 40 TB of backup data ? Does anybody use for example a "Data Domain DD460" or other systems using COS to reduce the amount of data. Thanks for help Chris ---------------------------------------------------------------------- This e-mail, including any attached files, may contain confidential and privileged information for the sole use of the intended recipient. Any review, use, distribution, or disclosure by others is strictly prohibited. If you are not the intended recipient (or authorized to receive information for the intended recipient), please contact the sender by reply e-mail and delete all copies of this message.
-- Paul Zarnowski Ph: 607-255-4757 Manager, Storage Systems Fx: 607-255-8521 719 Rhodes Hall, Ithaca, NY 14853-3801 Em: [EMAIL PROTECTED]
