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Update docs to say you need fsync to make sync rep work fast.

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This commit is contained in:
Simon Riggs 2011-03-22 16:23:54 +00:00
parent 8df08c8489
commit 6e8e7cc580
1 changed files with 7 additions and 1 deletions
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8
doc/src/sgml/high-availability.sgml
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@ -947,7 +947,7 @@ synchronous_replication = on
<para>
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
<varname>wal_receiver_status_interval</> is set to zero on the standby.
If the standby is the first matching standby, as specified in
<varname>synchronous_standby_names</> on the primary, the reply
@ -1013,6 +1013,12 @@ synchronous_replication = on
the rate of generation of WAL data.
</para>
<para>
Replies are only sent when WAL is written to disk, so setting
<varname>fsync</> to <literal>off</> on the standby will significantly
reduce performance of synchronous replication and should be avoided.
</para>
</sect3>
<sect3 id="synchronous-replication-ha">