ADSM-L

Using FILE instead of DISK devclass to avoid disk under-utilization

2006-10-25 12:20:30
Subject: Using FILE instead of DISK devclass to avoid disk under-utilization
From: Daniel Clark <dclark AT POBOX DOT COM>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Wed, 25 Oct 2006 11:49:02 -0400
I just got a situation that requires yet another storage pool
hierarchy, and I am starting to run into the problem described in [1];
basically I have more than enough disk in aggregate to handle nightly
backup loads, but when partitioned between different disk-based
storage pools, on a nightly basis some of them are hardly used at all,
while others are above capacity, forcing a migration to tape.

An elegant solution using disk in the FILE rather than DISK devclass
is presented in [2]:

When I get my new disk in, I plan to make a single RAID5 volume, and make a
directory on it for a FILE devclass.  I'll permit something large like 50
mounts on that class, and I'll make the volume size somewhere around 250M.

I'll define stgpools against this devclass, and I'll control their peak size
with MAXSCRATCH directives.  My 2G stgpool will have maxscratch=8, and so on.

This will give me most of the speed of my current solution (minus the RAID
overhead) and permit the stgpools to grow and shrink as demand varies.

However in [3] there is anecdotal evidence that for undefined reasons,
this just doesn't work well; however these messages are from 2000 /
ADSMv3, so I am wondering if anyone has any recent experience with
this kind of setup in TSM 5.2 or 5.3.

[1] Re: one stgpool migrates to two?
http://msgs.adsm.org/cgi-bin/get/adsm98/2564.html

[2] alternate plan for DASD primary pools...
http://msgs.adsm.org/cgi-bin/get/adsm0008/64.html

[3] Re: alternate plan for DASD primary pools...
http://msgs.adsm.org/cgi-bin/get/adsm0008/64/1.html

Thanks,
--
Daniel Joseph Barnhart Clark
http://www.pobox.com/users/dclark