@@ -947,7 +947,7 @@ synchronous_replication = on
947947 <para>
948948 After a commit record has been written to disk on the primary the
949949 WAL record is then sent to the standby. The standby sends reply
950- messages each time a new batch of WAL data isreceived , unless
950+ messages each time a new batch of WAL data iswritten to disk , unless
951951 <varname>wal_receiver_status_interval</> is set to zero on the standby.
952952 If the standby is the first matching standby, as specified in
953953 <varname>synchronous_standby_names</> on the primary, the reply
@@ -1013,6 +1013,12 @@ synchronous_replication = on
10131013 the rate of generation of WAL data.
10141014 </para>
10151015
1016+ <para>
1017+ Replies are only sent when WAL is written to disk, so setting
1018+ <varname>fsync</> to <literal>off</> on the standby will significantly
1019+ reduce performance of synchronous replication and should be avoided.
1020+ </para>
1021+
10161022 </sect3>
10171023
10181024 <sect3 id="synchronous-replication-ha">