Re: dbmirror

From: Gregory Wood <gwood(at)ewebengine(dot)com>
To: Andrew Sullivan <ajs(at)crankycanuck(dot)ca>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: dbmirror
Date: 2004-05-13 20:10:34
Message-ID: 40A3D63A.6060301@ewebengine.com
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Does dbmirror do that? No, it does not. It also doesn't support
promoting a slave database to a master; that has to be done manually, so
I wouldn't consider that too big a problem.

Worse in my opinion is that sequences don't get updated... so a slave
that tries to do an insert on a replicated table (for example, when it
gets manually promoted to master) will find the sequence not where the
master left it, but where it was loaded. Every sequence has to be
manually updated before the database is usable.

dbmirror was never intended to be anything but a poor man's
replication... and it worked remarkably well for that purpose. Now it's
time to look forward to Slony-I :)

Greg

Andrew Sullivan wrote:
> On Wed, May 12, 2004 at 05:53:05PM -0700, Gregory S. Williamson wrote:
>
>>Fred --
>>
>>Yes, the slave database(s) can be safely used in a R/O mode,
>
>
> Does it also block write transactions in those slaves? The ability
> for clients to write into the slave replicated tables is a problem,
> because it makes promoting a slave node somewhat risky.
>
> Slony-I has a trick to solve this problem, BTW.
>
> A
>

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