Re: Configuring synchronous replication

On Fri, 2010-09-17 at 21:43 +0900, Fujii Masao wrote:
> On Fri, Sep 17, 2010 at 5:09 PM, Heikki Linnakangas
> <heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
> > * Quorum commit. Wait until n standbys acknowledge. n=1 and n=all servers
> > can be seen as important special cases of this.
>
> I think that we should skip quorum commit at the first phase
> because the design seems to be still poorly-thought-out.

Agreed

> I'm concerned about the case where the faster synchronous standby
> goes down and the lagged synchronous one remains when n=1. In this
> case, some transactions marked as committed in a client might not
> be replicated to the remaining synchronous standby yet. What if
> the master goes down at this point? How can we determine whether
> promoting the remaining standby to the master causes data loss?

In that config if the faster sync standby goes down then your
application performance goes down dramatically. That would be fragile.

So you would set up like this
master - requests are > async
standby1 - fast - so use recv | fsync | apply
standby2 - async

So if standby1 goes down we don't wait for standby2, but we do continue
to stream to it.

--
Simon Riggs www.2ndQuadrant.com
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