Andrew Carlson wrote: > I know that the recommendation is to use as many physical volumes as > possible. In the near future, volumes are going to become available to > me to use as many as 15 volumes per database instance. > > Here is what I am wondering. It seems that, if I create a 5GB volume > per disk, for a total of 75GB capacity, that TSM would tend to write to > one volume for quite some time if it were JBOD. If I made it striped, > if I understand striping correctly, it will put the first chunk on the > first disk, second chunk on the second disk, etc. Then create one large > DB vol, which will effectively be spread across multiple volumes without > me having to make sure of the housekeeping. > > Any ideas, or real world experience? >
The TSM database has inherently a tendancy to 'stripe'. That is, after a few months of use, even on a jbod you'll see all disks used equally often. Now if you lose one disk in a raid-0, you'll lose the whole FS, thus all of you db volumes. If you have multiple raid-sets (or jbod) you'll just loose one db volume, which might make recovery a lot faster (depending on logmode settings and mirroring). I have the feeling that raid-0 might even slow TSM performance down when compared to JBOD. At best, I can't think of any advantage of raid-0. > For the record, in case anyone asks, I will be at TSM5.3 by the time I > do this, using a Fastt700 for the database volumes. > > Thanks! -- Met vriendelijke groeten, Remco Post SARA - Reken- en Netwerkdiensten http://www.sara.nl High Performance Computing Tel. +31 20 592 3000 Fax. +31 20 668 3167 "I really didn't foresee the Internet. But then, neither did the computer industry. Not that that tells us very much of course - the computer industry didn't even foresee that the century was going to end." -- Douglas Adams
