Just for the record, IBM doesn't unconditionally recommend database
mirroring (aka "The old scare tactics").  In the admin guide the section on
"roll-forward recovery" states 'roll-forward recovery is an alternative to
database mirroring'.  If you go this way you should mirror the log.  This
is the way I run my server and I am saving 28 gig of 3390-3 disks.

Bill Colwell
The Charles Stark Draper Laboratory
Cambridge Ma.
_________________________Reply Header_________________________
Author: ADSM-L AT vm.marist DOT edu
Subject: Re: ADSM mirroring vs. AIX mirroring
01-06-1998 09:17 AM

Wow, this sounds suspiciously like the old scare tactics that would cause
folks to buy a ton of hardware!!  To double your capacity just so that you
"have a prayer that a bad write during ADSM crashed" only got propogated
to 1 of the mirrored sets, is unjustified.  Since ADSM is stable
program-wise, if that improbable corruption occurred, how about using the
recovery procedures?  MassMutual hasn't had ANY corruption of DB's
(crossed fingers) in the last 2 years.  Think of how much mainframe DASD
we've saved.  If this philosiphy was common practise,, would we have to
mirror DB2 and other DB's??  Yikes, there goes the hardware budget!!!!!!!

> -----Original Message-----
> From: Pittson, Timothy ,HiServ/NA [SMTP:tpittson AT HIMAIL.HCC DOT COM]
> Sent: Monday, January 05, 1998 11:45 AM
> To:   ADSM-L AT VM.MARIST DOT EDU
> Subject:      Re: ADSM mirroring vs. AIX mirroring
>
> Joe,
>         If it comes down to using ADSM or AIX to mirror the database,
> I'd use
> ADSM mirroring.  I think the big advantage to using ADSM mirroring is
> in
> the event of the system crashing during a DB write and causing DB
> corruption.  With AIX mirroring, I think you're SOL but with ADSM
> mirroring, if the write didn't complete to both copies of the DB, you
> stand a chance of one copy of the database not being corrupted.
> Regarding RAID, I had posted questions to the ADSM-L listserver a
> couple
> of years ago about this and received some very helpful information -
> somebody had even done some benchmarking (7137 array vs. SCSI vs. SSA
> or
> something like that - this was a long time ago - at the time, the 7137
> outperformed the other options ).  We decided on using a dedicated
> 7137-514 disk array configured for RAID-5 w/hot spare for our ADSM DB
> (16 GB) and have been very happy with the performance.  There had also
> been some posts about using mirroring/striping with SSA disks but I
> don't know what the results of that were.  I keep the recovery logs on
> separate dedicated SSA disks and use ADSM mirroring to mirror them.
>
> Tim Pittson
>
>
> >-----Original Message-----
> >From:  Joe Morris [SMTP:morris AT UNC DOT EDU]
> >Sent:  Monday, January 05, 1998 10:49 AM
> >To:    ADSM-L AT VM.MARIST DOT EDU
> >Subject:       ADSM mirroring vs. AIX mirroring
> >
> >I've been browsing through the ADSM archives at Marist and could not
> find
> >what I was looking for.  Setting up a new server that has ample space
> to
> >replace our old ADSM server.
> >
> >What are the pros and cons of using ADSM and AIX to mirror the
> database
> >and log volumes.  Mainly focusing on differences between using AIX
> >mirroring and the built-in mirroring in ADSM.
> >
> >I had considered a RAID configuration, but it seems like that is not
> such
> >a hot solution for the database for performance reasons.  Am I wrong?
> >
> >_______________________________________________________________
> >Joe Morris  -  morris AT unc DOT edu  -  http://sunsite.unc.edu/morris
> >Academic Technology and Networks, Development and Eval Services
> >University of North Carolina at Chapel Hill      PGP by request