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Subject:	Mirroring Question
From:	Adam Slesinger <aslesinger AT us.bnsmc DOT com>
To:	storman AT us.ibm DOT com
Date:	Mon, 07 Dec 1998 11:45:16 -0500

Andy,

    Saw your e-mail concerning ADSM mirroring vs. AIX mirroring.  I was
wondering if you suggest using ADSM mirroring instead of RAID 5 on SSA
as well.  We are starting the implementation of ADSM at our plant today
but have come to a standstill because we are not sure which way to set
up our eight 9GB disks which will be used as the primary storage pool.
We have heard the arguments from both sides and were hoping that you
might be able to lend some of your knowledge on this subject.
    Thanks very much for your time,

Sincerely,
adam
_______________
Adam Slesinger
Corporate Information Systems
Brown & Sharpe, RI
Phone: (401) 886-2236
Email: aslesinger AT us.bnsmc DOT com


I definitely recommend using ADSM mirroring, *not* AIX mirroring. One m=

 ain
 reason for this has to do with database volume corruption. If, for
some=
  reason,
 one of your ADSM DB volumes becomes corrupted, AIX mirroring will pass
=
 the
 corruption on to the mirrored copy while ADSM may not pass on that
corr=
 uption.
 For example, if ADSM or AIX crashes in the middle of a write to the
dat=
 abase,
 one of the volumes may be corrupted due to the partial write. With AIX
 mirroring, this corruption will be passed to the mirror and you will
be=
  in a
 database recovery situation. With ADSM mirroring, the other (mirror)
vo=
 lume may
 not be corrupted. ADSM could then be started and the ADSM mirroring
wou=
 ld
 (correctly) resynchronize the mirrored volumes.

 Andy Raibeck
 ADSM Level 2 Support



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