ADSM-L

Re: Performance Large Files vs. Small Files

2001-02-14 15:52:38
Subject: Re: Performance Large Files vs. Small Files
From: Richard Sims <rbs AT BU DOT EDU>
Date: Wed, 14 Feb 2001 15:52:59 -0500
>I believe you change the buffer pool size in the dsmserv.opt file and use an
>entry as follows:
>BUFPOOLSIZE 16384
>The accepted way to do this is to note your current buffer pool size and then
>double it. Watch your cache hit percentage for a day or two and then double
>again to achieve the optimal server performance with should be attained when
>the cache hit percentage is stable and above 99 percent...

By all means pursue this.  But...as the ADSM Performance Tuning Guide pointed
out (http://www.tivoli.com/support/storage_mgt/adsm/pubs/admanual.htm#perfV3)
you should not do this without observing realities in your operating system.
You can certainly achieve very high Cache Hit ratios and still have crummy
performace - because the caching is happening in virtual storage.  We
recently saw a posting from a customer with a 70 GB database and only 512 MB
for the server system - a tight squeeze at best, considering all the other
memory requirements in running a server system.  Server systems need abundant
memory.

This all boils down to capacity planning and being realistic about what can be
achieved in the current system's configuration.  You need to consider much
more than TSM, in that it's just one passenger demanding service on the cruise
ship.

   Richard Sims, BU