Date:     November 29, 1999             Time: 9:02 AM
From:     Jerry Lawson
          The Hartford Insurance Group
(860)  547-2960          jlawson AT thehartford DOT com
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The guy who handles MVS Performance came to me with the some concern over the
The guy who handles MVS Performance came to me with the some concern over the
DASD response that ADSM was getting - specifically with our storage pool
volumes.  We did some analysis, and of course determined that the response
problems were mapping to the times when migrations or storage pool backups
were running.  I asked him to write up what he saw as a question that we
could post to the list.  Here is his observation:

Our ADSM server storage pool is spread over 25 separate DASD volumes across 5
different SVAs (Shared Virtual Array).  During our backup and migration
processes, we appear to get very poor response time for these DASD volumes.
At sustained I/O rates of 1 to 1.5 I/Os per second spread across all of the
pool volumes, our DASD response times for these volumes consistently rides at
our above 150 milliseconds.  Two thirds of this appears to be DISCONNECT with
the other portion attributable to CONNECT for the most part.  Device
utilization for these volumes appears to ride around 15%.  These DASD volumes
compare very poorly - performance-wise - to the rest of our DASD farm.

Do you have any thoughts or suggestions as to how we may address this or do
you believe that this is simply a by-product of the product's normal
workings.  Any suggestions would be appreciated.
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I should probably add that the SVA is the latest and greatest STK DASD - the
I should probably add that the SVA is the latest and greatest STK DASD - the
next upgrade after the RVA vesrion that IBM marketed.  We use 3380K images as
the device types, for a total of 34GB of DASD.  I should note that during
this same time, the DB, which is also mapped over the same set of devices,
does not have a response problem.


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                                                     Jerry
                                                     Jerry