ADSM-L

Re: Trouble when TSM-database reaches 100Gb?

2005-09-01 09:43:07
Subject: Re: Trouble when TSM-database reaches 100Gb?
From: Paul Zarnowski <psz1 AT CORNELL DOT EDU>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Thu, 1 Sep 2005 09:42:36 -0400
The limit of 100GB isn't cast in stone - it's a rule of thumb that
I've heard tossed about frequently.  The actual fall-off in
performance will depend a lot on your disk subsystem.  Faster RPM
drives can help, as well as spreading the I/O across more spindles
(i.e., striping), use of write-cache, etc.

When you reach this limit, the performance degradation can happen
fairly quickly.  Keep your eye on expiration.  If you can't expire
objects out of your database in the time you have allotted to this,
then your database size can start ballooning, causing a negative
feedback loop.  Performance will continue to deteriorate quickly from
this point.

We took the road of getting bigger and faster servers for years,
before we finally fell off the cliff.  Keep in mind that you don't
have to necessarily add another physical server.  On AIX, we run
multiple TSM server instances, all on the same AIX box, primarily to
keep the database sizes down.

Another factor to consider, besides performance, is
recoverability.  If you ever have to restore or audit your database,
a larger database can be a serious problem.

..Paul

At 04:16 AM 9/1/2005, Hans Christian Riksheim wrote:
Hello,

we are experiencing throughput problems on our TSM-installation. Apart
from he obvious that we have too few tape drives, bottlenecks in our LAN
and an old AIX-box, we got a suggestion to add another TSM-server. The
reason was that the performance degrades when the TSM-database reaches
about 100Gb in size.

We find it a little troublesome to add a new TSM server every time we
reach 100 Gb, we would rather just buy us a new AIX-box which is 5 times
faster.

So I ask you if this 100 Gb limitiation really applies. What is your
experience with this?


Server version 5.2.3.3
Ca. 100 clients.


Best regards

Hans Chr. Riksheim


--
Paul Zarnowski                            Ph: 607-255-4757
Manager, Storage Systems                  Fx: 607-255-8521
719 Rhodes Hall, Ithaca, NY 14853-3801    Em: psz1 AT cornell DOT edu