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 <jdtan AT med.cornell DOT edu>
 Reply-To: "ADSM: Dist Stor Manager" <ADSM-L AT vm.marist DOT edu>
 To: ADSM-L AT vm.marist DOT edu
 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
 ><MTailor AT CARILION DOT COM> 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