Re: Sync Rep: First Thoughts on Code

On Fri, 2008-12-05 at 12:09 +0900, Fujii Masao wrote:

> On Thu, Dec 4, 2008 at 6:29 PM, Simon Riggs <simon@2ndquadrant.com> wrote:
> > The only sensible settings are
> > synchronous_commit = on, synchronous_replication = on
> > synchronous_commit = on, synchronous_replication = off
> > synchronous_commit = off, synchronous_replication = off
> >
> > This doesn't make any sense: (does it??)
> > synchronous_commit = off, synchronous_replication = on
> 
> If the standby replies before writing the WAL, that strategy can improve
> the performance with moderate reliability, and sounds sensible.

Do you think it likely that your replication time is consistently and
noticeably less than your time-to-disk? If not, you'll wait just as long
but be less robust. I guess its possible.

On a related thought: presumably we force a sync rep if forceSyncCommit
is set?

> IIRC, MySQL Cluster might use that strategy.

Not the most convincing argument I've heard.

-- Simon Riggs           www.2ndQuadrant.comPostgreSQL Training, Services and Support