ADSM-L

Re: ADSM dasd pool migration

1998-09-09 09:43:11
Subject: Re: ADSM dasd pool migration
From: Jeff Connor <connorj AT NIMO DOT COM>
Date: Wed, 9 Sep 1998 09:43:11 -0400
Add mine too.  This is one of my biggest pet peeves.. I have my disk pool
thresholds at hi=80 lo=65 on a 70GB disk pool.  Migration is to four 3590
tape drives in an STK Silo. Backups fill my disk pool faster than it can
migrate to tape sometimes reaching 100% utilization.  Sad part is when
migration catches up, and disk pool utilization drops below my high
threshold of 80%, many backup sessions remain in mediaw status, some for
hours. Even when pool utilization falls below the low value of 65% there
always seems to be at least one, of the four max migrations processes, that
keeps running and doesn't end until the pool is nearly or completely empty.
My temporary work around was to define a second tape pool and automatically
issue an admin command to update the nextpool value for the disk pool
swapping tape pools every half hour daily from 23:00 to 7:00am. This seemed
to work fairly well although I had some intermittent server hangs that I
suspected might be caused by my frequent changes to the migration hierachy.
My long term solution is to add 4 more 3590 tape drives to the silo and
double the size of my disk pool which I finally got management to approve..
It would be nice if the ADSM server could periodically re-check disk pool
utilization and re-route the backup sessions to disk if pool utilization
has dropped. It should stop sending sessions directly to tape that could
have fit on disk..


Jeff





Dwight Cook <decook AT AMOCO DOT COM> on 09/08/98 04:58:05 PM

Please respond to "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>

To:   ADSM-L AT VM.MARIST DOT EDU
cc:    (bcc: Jeffrey P Connor/IT/NMPC)
Subject:  Re: ADSM dasd pool migration




     Nice to see I'm not alone...
     But just wait until you have all 50 clients in a media wait and your
     tape drives manage to clear the diskpool and you are watching about
     40-ish clients still in media wait with an EMPTY DISK POOL !
     Yes, I've had disk pools fill and all the inbound sessions call for
     tape mounts, then the migration processes clear the diskpool and there
     ain't no way to point those specific sessions back over to the
     diskpool.
     I even tried pointing my tapepool's "nextpool" over to my diskpool
     (yes, I removed diskpool's next of tapepool first) in hopes that when
     the next tape swap took place that the other jobs waiting on mounts
     might recalculate their needs and see they could go to a nice empty
     diskpool BUT NO!

     anyway, just adding my 2 cents worth

     later,
           Dwight


______________________________ Reply Separator
_________________________________
Subject: ADSM dasd pool migration
Author:  jack.revette (jack.revette AT dowcorning DOT com) at unix,mime
Date:    9/8/98 2:20 PM


Had 10 GB dasd storage pool backed up by a 3590 tape storage pool (one
thread, migration threshholds set at 0% - 70%).  After some recent
improvements in the server (AIX Server Version 3, Release 1, Level 1.5)
and the network, believe I encountered for the first time a situation in
which I could fill the dasd storage pool faster than I could migrate it.
I have 3 tape drives and 50+ clients.  So if I had 25 clients active
backing up data to the disk storage pool, when it filled, one tape drive
was in use for a migration, and the other two would be allocated for
client backups (ADSM was 'smart' (??) enough to recognize that there was
no room on disk, so let's go to the next pool - tape).  The other 23
clients went into media wait status waiting for a mount point.  When the
migration processed reached an end of volume condition, one of the other
23 clients in a media wait status 'stole' the migration mount point,
making the situation worse rather than better. (i.e. if migration
maintains priority, other 23 clients will be able to backup to disk,
as/once migration completes).
I've opened an ETR (33873,422) with IBM, and the response is that
backups have priority over migration and this cannot be changed.  I've
been requested to submit a product Design Change Request.  I'm very
willing to do this, but just wanted to pass this by the users and
developers on the listserv to make sure I'm on the right track.
(By the way, I've put some circumventions in place - dasd storage pool
is now 20 GB, largest client will now backup directly to tape, there are
now 2 threads on the migration).

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