Date: Fri, 26 Jan 2018 10:37:38 +0900
From: Michael Paquier <michael.paquier@gmail.com>
To: Stephen Frost <sfrost@snowman.net>
Cc: Azimuddin Mohammed <azimeiu@gmail.com>,
	Rakesh Kumar <rakeshkumar464@aol.com>, pgsql-admin@postgresql.org,
	pgsql-general@postgresql.org
Subject: Re: Sync replication
Message-ID: <20180126013738.GG17847@paquier.xyz>
References: 
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 <CAKUuFd5GCiJip8q8QOMQL0bZUBDbGnXTNJVxoLzhKe0+nwZo_w@mail.gmail.com>
 <20180126012143.GB2416@tamriel.snowman.net>
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On Thu, Jan 25, 2018 at 08:21:43PM -0500, Stephen Frost wrote:
> That's correct, which is why it's encouraged to have multiple replicas
> configured when using synchronous replication.  In v10, it's possible to
> specify how many synchronous replicas are required to have acknowledged
> a given transaction before a COMMIT is returned to the applicaiton.
> Please review the documentation here:
>=20
> https://www.postgresql.org/docs/current/static/warm-standby.html#SYNCHRON=
OUS-REPLICATION

Be careful about the performance impact if there is network latency
between a primary and its standbys. One small correction to what Stephen
says here. It is possible to define multiple synchronous standbys in
v9.6. v10 has added the possibility to define quorum groups. Note that
the grammar as been kept backward-compatible across versions.
--
Michael

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