Ours are SCSI-attached external subsystem (2104). Wow... from 1 MB/min to 20 MB/sec! We are definitely going to investigate raw devices!
johnn >can I just ask, are these drives external attached on a SCSI array types >or internal to the box, (I mean internal bays) depending on the server!? > >'cause I have similar situation, when we went into using T3 storage for db >and spools. The inherent limitation to configure T3's as raw or JBOD >there was as significant slowness in performance. Yes at first we were using >filesystems. we saw 1meg a min :( > >After going to raw disks we saw 20 - 25 MB /sec writes. Which >is still way less than what a T3 is advertized to do though (80MB >sustained). Oh well may be T3 's were not a right storage for TSM is what >I have learnt. Offcourse with 256MB cache and write ahead enabled. > >I was told that the TSM server uses variable 4 to 64k and the T3 with 64K >fixed block size was also the cause for the low performance .. > >-Chetan > > > > > >On Thu, 26 Sep 2002, Johnn D. Tan wrote: > >> Date: Thu, 26 Sep 2002 12:42:45 -0400 >> From: Johnn D. Tan <[EMAIL PROTECTED]> >> Reply-To: "ADSM: Dist Stor Manager" <[EMAIL PROTECTED]> >> To: [EMAIL PROTECTED] >> Subject: Re: Disk volumes >> >> I have 12 36-GB drives available for spool. >> >> Based on recommendations made to this list earlier this year, I went >> with 12 mirrored disk spools of 16 GB each (keep in mind disk >> overhead). >> >> As I understood it, the issue was you want many spools so that, as >> Allen mentioned, you can have many threads for backups and even >> migrations (assuming you have a good number of tape drives). >> >> However, you don't want so many spools per disk, otherwise there is >> contention for head movement on the drive which would result in >> poorer performance. >> >> johnn >> >> >> >> >=> On Thu, 26 Sep 2002 08:54:01 -0400, Mahesh Tailor >> ><[EMAIL PROTECTED]> said: >> > >> >> Hopefully this is a simple question: I have fourteen 36GB >>drives that are >> >> available for the diskpool and I was wondering whether it is >>better to have >> >> seven 5GB files or three 10GB files or one 35GB file or >>something else? The >> >> drives are mounted in two IBM-2014 Ultra-Wide SCSI disk drawers with >> >> separate Ultra-Wide contollers. The other 14 drives are used >>for DB, LOG, >> >> and spare. >> > >> >You have a total of 28 spindles, 14 each on two busses, right? >> > >> >I'd suggest making a RAID-5 out of the fourteen free spindles, >>and then make >> >the individual volumes "A reasonable size". What's a reasonable size? >> >Uh... ;) >> > >> >I just did this with a drawer of 36G SSA, and I chose 10G >>volumes, because I >> >have about a dozen (and growing) disk pools amongst which I need to divide >> >things up. >> > >> >Even if you only have one or two disk pools, it's useful to have >>more than a >> >few volumes per pool, because instantaneously only on thing can write to a > > >volume at a time. So, for example, if you have 12 clients >backing up, and one > > >70G disk volume, there is contention for the thread controlling that one >> >volume. >> > >> >So calculate the size so that you'll have as many volumes as you feel like >> >keeping track of, but not many more than that. >> > >> > >> >- Allen S. Rout >>
