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.
Orville L. Lantto
Glasshouse Technologies, Inc.
________________________________
From: ADSM: Dist Stor Manager on behalf of Richard Sims
Sent: Wed 4/25/2007 09:22
To: ADSM-L@VM.MARIST.EDU
Subject: Re: [ADSM-L] TSM only reads from COPY1 during DB backup
On Apr 24, 2007, at 3:23 PM, Orville Lantto wrote:
> Has anyone else observed that TSM only reads from COPY1 of a db
> volume mirror pair during DB backup?
Why do you believe it should do otherwise? As exposited in the Admin
Guide manual, mirroring is for disk failover purposes. You can
artificially cause both mirrors to be read, via MIRRORRead Verify,
but that's for paranoid circumstances rather than standard operation,
and exacts a performance penalty.
Richard Sims
