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doc: various updates

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Ian Barwick
2019-03-13 16:55:32 +09:00
parent 617e466f72
commit 5f92fbddf2
4 changed files with 24 additions and 107 deletions
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doc/repmgrd-automatic-failover.sgml
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@@ -27,13 +27,13 @@
<title>Using a witness server with repmgrd</title>
<para>
In a situation caused e.g. by a network interruption between two
data centres, it's important to avoid a "split-brain" situation where
data centres, it's important to avoid a &quot;split-brain&quot; situation where
both sides of the network assume they are the active segment and the
side without an active primary unilaterally promotes one of its standbys.
</para>
<para>
To prevent this situation happening, it's essential to ensure that one
network segment has a "voting majority", so other segments will know
network segment has a &quot;voting majority&quot;, so other segments will know
they're in the minority and not attempt to promote a new primary. Where
an odd number of servers exists, this is not an issue. However, if each
network has an even number of nodes, it's necessary to provide some way
@@ -41,13 +41,19 @@
</para>
<para>
This is not a fully-fledged standby node and is not integrated into
replication, but it effectively represents the "casting vote" when
replication, but it effectively represents the &quot;casting vote&quot; when
deciding which network segment has a majority. A witness server can
be set up using <xref linkend="repmgr-witness-register">. Note that it only
makes sense to create a witness server in conjunction with running
<application>repmgrd</application>; the witness server will require its own
<application>repmgrd</application> instance.
be set up using <link linkend="repmgr-witness-register"><command>repmgr witness register</command></link>;
see also section <link linkend="using-witness-server">Using a witness server</link>.
</para>
<note>
<para>
It only
makes sense to create a witness server in conjunction with running
<application>repmgrd</application>; the witness server will require its own
<application>repmgrd</application> instance.
</para>
</note>
</sect1>