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Re: beta testing version

From: Don Baccus <dhogaza(at)pacifier(dot)com>
To: The Hermit Hacker <scrappy(at)hub(dot)org>, xuyifeng <jamexu(at)telekbird(dot)com(dot)cn>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: beta testing version
Date: 2000-11-30 23:35:54
Message-ID: 3.0.1.32.20001130153554.01ab16f0@mail.pacifier.com (view raw or flat)
Thread:
Lists: pgsql-hackers
At 07:02 PM 11/30/00 -0400, The Hermit Hacker wrote:
>
>v7.1 should improve crash recovery for situations like this ... you'll
>still have to do a recovery of the data on corruption of this magnitude,
>but at least with the WAL stuff that Vadim is producing, you'll be able to
>recover up until the point that the power cable was pulled out of the wall

No, WAL won't help if an actual database file is corrupted, say by a
disk drive hosing a block or portion thereof with zeros.  WAL-based
recovery at startup works on an intact database.

Still, in the general case you need real backup and recovery tools.
Then you can apply archives of REDOs to a backup made of a snapshot
and rebuild up to the last transaction.   As opposed to your last
pg_dump.

So what about mirroring (RAID 1)?  As the docs tell ya, that protects
you against one drive failing but not against power failure, which can
cause bad data to be written to both mirrors if both are actively 
writing when the plug is pulled.

Power failures are evil, face it! :)



- Don Baccus, Portland OR <dhogaza(at)pacifier(dot)com>
  Nature photos, on-line guides, Pacific Northwest
  Rare Bird Alert Service and other goodies at
  http://donb.photo.net.

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Subject: Re: beta testing version
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