From: | Josh Berkus <josh(at)agliodbs(dot)com> |
---|---|
To: | postgres hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Standbys which don't synch to disk? |
Date: | 2011-05-11 18:48:18 |
Message-ID: | 4DCAD9F2.4030905@agliodbs.com |
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Lists: | pgsql-hackers |
Robert,
> > That WAL has effectively disappeared from the
> > master, but is still present on the slave. Now the master comes up
> > and starts processing read-write transactions again, and generates a
> > new and different 1kB of WAL. Hilarity ensues, because the two
> > machines are now out of step with each other.
Yeah, you'd need some kind of instant failover and STONITH. That is,
any interruption on the master would be a failover situation. While
that seems conceivable for crashes, consider that a planned restart of
the master might be an issue, and an OOM-kill would certainly be.
> > You could possibly fix this by making provision for the master to
> > connect to the slave on start-up and stream WAL "backwards" from slave
> > to master. That'd be pretty spiffy.
Ouch, now you're making my head hurt.
--
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com
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