Hi Robin, We use STK 9840 drives in an STK9710 robot (forerunner of the L700, I think). Mount time for the 9840 is under 30 seconds; maybe 40 seconds to write for an append. Dismount is also very fast because they rewind to the middle of the tape instead of the beginning, I think.
The faster drives make running collocation quite painless; even if you have to mount 10 tapes on a restore, that only adds 5 minutes total to the restore time. The 9840 is in the same class as the IBM 3590 drive; MUCH faster to mount and locate than DLT. (and yep, lots more $) We tried DLT drives in the 9710 first. Worked OK for our low-volume TSM server; just couldn't take the pounding on our high-volume TSM server. We especially got hurt by the DLT "false cleans". Too much start/stop/append activity on the tapes made them subject to I/O errors on readback; each time you get an I/O error it triggers a false clean; so doing the restore you get up to 3 minutes to mount, plus another 3-6 minutes to process the cleaning tape after the tape dismounts! That was a killer. Your mileage may vary.... ************************************************************************ Wanda Prather The Johns Hopkins Applied Physics Lab 443-778-8769 [EMAIL PROTECTED] "Intelligence has much less practical application than you'd think" - Scott Adams/Dilbert ************************************************************************ -----Original Message----- From: Robin Sharpe [mailto:[EMAIL PROTECTED]] Sent: Monday, December 17, 2001 1:59 PM To: [EMAIL PROTECTED] Subject: Re: Incremental forever -- any problems? That's interesting... what kind of tape drives? We have two DLT libraries: An ATL P3000 and AN HP 20/700 (rebadged STK L700). The ATL has rather slow robotics, but is very reliable. The HP has somewhat faster robotics, but for some reason takes much longer to label new tapes. I think the major bottleneck is the tapes... DLTs take a long time to mount... at least 90 seconds, usually more like 2 minutes. If you are appending to the end of the tape, even longer... and that does not necessarily correspond to percentage full, because DLT is serpentine; it writes to the end of tape, then back to the front several times. So if you need, say, two dozen tape mounts for a restore (which is not uncommon), that could easily add an hour to the restore time. Robin Sharpe Berlex Labs "Prather, Wanda" <Wanda.Prather@J HUAPL.EDU> To: [EMAIL PROTECTED] cc: (bcc: Robin Sharpe/WA/USR/SHG) 12/17/01 11:18 Subject: AM Re: Incremental forever -- any problems? Please respond to "ADSM: Dist Stor Manager" We have the opposite situation - we have fast robotics and use collocation. With collocation on fast tape, it doesn't matter whether you are doing 2 weeks or 2 years of data, a restore takes the same amount of time. Doing periodic fulls doesn't "refresh" anything, from TSM's point of view - the original backups are still in the TSM DB and still available, even if they are 5 years old. If you do periodic fulls, you have to retransmit everything over the network again, and you have to adjust your policies to make sure you allow those redundant versions to be kept; you increase the size of your DB and the amount of reclaims you have to do. Doing periodic "fulls" would do nothing whatever for us, except bog down the network. I suggest you try doing a large restore to test your own capabilities. If you can't restore in a timely fashion, FIRST figure out what your bottleneck is before you decide to "fix" it by doing full backups. Then if you find out you still can't do restores in a timely fashion, at least check out the use of BACKUPSETS. They give you all the client's active data on one tape, without retransmitting all the data, and without creating an extra zillion entries in your DB.
