Re: Standbys which don't synch to disk?

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