Re: [ADSM-L] TSM only reads from COPY1 during DB backup

2007-04-25 11:49:43
Subject: Re: [ADSM-L] TSM only reads from COPY1 during DB backup
From: Richard Sims <rbs AT BU DOT EDU>
Date: Wed, 25 Apr 2007 11:49:10 -0400
On Apr 25, 2007, at 10:55 AM, Orville Lantto wrote:

Reads should be safe from mirrored volumes and are commonly done in
operating systems to load  balance.  Not taking advantage of the
available IO resource is wasteful and puts an unnecessarily
unbalanced load on an already IO stressed system.  It slows down db
backups too.
Then your issue is performance, rather than database voracity.
This is addressed by the disk architecturing chosen for the TSM
database, where raw logical volumes and RAID on top of high
performance disks accomplishes that.  Complementary volume striping
largely addresses TSM's symmetrical mirror writing and singular
reading.  Whereas TSM's mirroring is an integrity measure rather then
performance measure, you won't get full equivalence from that.
Another approach, as seen in various customer postings, is to employ
disk subsystem mirroring rather than TSM's application mirroring.  In
that way you get full duality, but sacrifice the protections and
recoverability which TSM offers.

   Richard Sims