[Fwd: LTO Fibre tape performance under AIX 5.1]

 As a followup to my earlier message, one issue that came up is the TSM
database and logs are on the same disks.  In other words, we have the
first copy of the database and the log on one disk, and the database
mirror and log mirror on another disk. They are all using separate
filesystems.  I don't think this will perform well, but the system admin
that set up the system insists on them that way because he doesn't want
to use the root volume group to hold the logs (the system only has 4
drives today, two for rootvg, and two for TSM stuff).  In a few weeks we
are supposed to be getting some SSA drives, but have to make do until then.
  Would having a 9GB database and 1GB log on the same disk cause
inordinate seek times? The server is in test now, with only a couple
clients on it, so they are only a few percent utilized.

John

-------- Original Message --------
Subject: LTO Fibre tape performance under AIX 5.1
Date: Mon, 16 Jun 2003 13:42:10 -0500
From: John Schneider <jdschn AT attglobal DOT net>
Reply-To: jdschn AT attglobal DOT net
To: ADSM: Dist Stor Manager <ADSM-L AT VM.MARIST DOT EDU>



Greetings,
   We are installing a new TSM server on a pSeries 650 using TSM
5.1.6.5, and a 3584 Tape Library with a L32 and D32 frames with 15 LTO
Gen 1 Tape drives.  The 650 has 4 2Gb/sec FC ports; two go one McData
Spherion 4500 switch, and to go to another.  Half the tape drives are go
to one Spherion switch, and half to the other.  We have them zoned so
that each FC adapter can only see 3 or 4 drives.
   Our problem is that we can't get the LTO performance where it
belongs.  A typical backup from the 650 itself using shared memory (or
not) only gets 5-6 MB/Sec.  About the same for a Giga-bit network AIX
client with no other load.
   Even a "MOVE DATA" tape-to-tape maxes out at 8 MB/sec.   In this
test, we made sure the two tape drives involved were on different FC
adapters, on different Spherion switches, and the 650 was otherwise
idle, so there should have been no contention anywhere.  It took 45
minutes to copy 21GB.  Not very good.
   The 3584 firmware is v3060, the 3580 firmware is v3481, both the
latest.  The 650, the 6228 (FC adapter) microcodes are also the latest.
The problem seems to be the same for all the drives.  We have bumped up
the dsmserv.opt options to appropriately high levels according to the
Performance Guide.  We think we have not overlooked anything there.

    Any suggestions certainly appreciated.

John Schneider

***********************************************************************
* John D. Schneider   Email: jdschn AT attglobal DOT net * Phone: 636-492-0247
* Lowery Systems, Inc.
* 1329 Horan                  Disclaimer: Opinions expressed here are
* Fenton, MO 63026                   mine and mine alone.
***********************************************************************




--
John Schneider

***********************************************************************
* John D. Schneider   Email: jdschn AT attglobal DOT net * Phone: 636-492-0247
* Lowery Systems, Inc.
* 1329 Horan                  Disclaimer: Opinions expressed here are
* Fenton, MO 63026                   mine and mine alone.
***********************************************************************