ADSM-L

Re: mirroring db and log

2000-05-04 15:55:10
Subject: Re: mirroring db and log
From: "Cook, Dwight E" <cookde AT BP DOT COM>
Date: Thu, 4 May 2000 14:55:10 -0500
IF the data in the file is corrupt the mirror will be identical to the other
and corrupt also...

Now, one thing that does come into play here is potential benefit from *SM
mirrored DB & LOG files when you use MIRRORWRITE LOG & DB as parallel
when it comes right down to it the speed difference between getting a write
to a RAID box or the first DB or LOG vol (thus allowing activity to
continue) is about like the difference in time to get to the close side of
the moon or the far side... that diff doesn't really matter...
BUT in your raid box do you have just one interface ? (and that is just one
raid box but probably does have redundant power...)
I mirror my DB & LOG via *SM and have the volumes for the primary (db&log)
and for the mirrors out different SSA cards and in different drawers of SSA
disks
I used to be real anal and make sure the cards were on different buss but
anymore I don't realy bother with that...if half the processor goes down I
don't think it will be running...

With all this hoot & poot you are only working towards processing speeds &
availability, not software corruption.

I do have two (of 12) environments that have raid boxes for the DB & LOG and
I only run a single copy...
I still have those environments because they have been around a long time,
we were trying something different at that time, and I just haven't gotten
around to switching them over to what I call "my current standard
configuration" simply 'cause they aren't broke !

does make administration a little tougher with the two odd ball
environments...
like send panic through me when I query the DB vol and only find ONE !

just my thoughts...
Dwight



> ----------
> From:         Gerald Wichmann[SMTP:gwichmann AT SANSIA DOT COM]
> Reply To:     ADSM: Dist Stor Manager
> Sent:         Thursday, May 04, 2000 2:21 PM
> To:   ADSM-L AT VM.MARIST DOT EDU
> Subject:      mirroring db and log
>
> The TSM book recommends mirroring the DB and log via TSM rather then AIX..
> If I throw my DB and log files on a RAID 5 array is there any point in
> mirroring it on the tsm level? For example in case one of the files
> becomes
> corrupt? Or is that a moot point with regular daily DB backups?
>
> Gerald Wichmann
> RS Engineer
> Sansia System Solutions
> 408-844-8893 work
> 408-844-9801 fax
>
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