From 6e8e7cc580665ddd43c8ca2acc6d60f345570a57 Mon Sep 17 00:00:00 2001 From: Simon Riggs Date: Tue, 22 Mar 2011 16:23:54 +0000 Subject: [PATCH] Update docs to say you need fsync to make sync rep work fast. --- doc/src/sgml/high-availability.sgml | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/doc/src/sgml/high-availability.sgml b/doc/src/sgml/high-availability.sgml index a7e2474189d..40b8b7393f8 100644 --- a/doc/src/sgml/high-availability.sgml +++ b/doc/src/sgml/high-availability.sgml @@ -947,7 +947,7 @@ synchronous_replication = on After a commit record has been written to disk on the primary the WAL record is then sent to the standby. The standby sends reply - messages each time a new batch of WAL data is received, unless + messages each time a new batch of WAL data is written to disk, unless wal_receiver_status_interval is set to zero on the standby. If the standby is the first matching standby, as specified in synchronous_standby_names on the primary, the reply @@ -1013,6 +1013,12 @@ synchronous_replication = on the rate of generation of WAL data. + + Replies are only sent when WAL is written to disk, so setting + fsync to off on the standby will significantly + reduce performance of synchronous replication and should be avoided. + +