ADSM-L

Response to the mirror log/DB responses

1996-12-03 12:33:33
Subject: Response to the mirror log/DB responses
From: Dave Sanders <DSanders AT MASSMUTUAL DOT COM>
Date: Tue, 3 Dec 1996 12:33:33 -0500
Previously I asked for feedback in regards to mirroring the logs and the
DB.  I've read the manual on that subject and it looks to me as if there
aren't ANY good reasons to continue to mirror the log and/or DB
--IF YOU HAVE THOSE DSN'S ON RAID DEVICES THAT HAVE BATTERY BACKUP OR A
RELIABLE UPS SYSTEM---.
RELIABLE UPS SYSTEM---.

The manual says:
Mirroring provides the following advantages:

    Protects against media failures within the database or recovery log by
    providing up to three exact copies.

    Continues database operations without interruption if a database or
    recovery log volume fails by using a mirrored copy of the failed
    volume.  The failed volume is placed offline and is automatically
    synchronized when brought back online.

    Provides a way to avoid costly database recoveries.

    Increases the database read performance by allowing the server to read
    data from any available volume copy.

**Raid devices virtually eliminate the media failures that can cause loss
of dsn access.
**Heavy-cached devices on a read should perform "as good as it gets" and
should also be quicker on writes (since it will only have to be written
once instead of waiting for the synchonization write) and will use
DASDFASTWRITE to cache and disconnect.

So, I should be able to see a performance IMPROVEMENT and resource savings
if I shut off mirroring,,,right??  Comments??
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