Commit ffa0e8f0 authored by Bruce Momjian's avatar Bruce Momjian

Add mention of shared-memory/disk for multi-master clustering.

parent 617f123f
<!-- $PostgreSQL: pgsql/doc/src/sgml/high-availability.sgml,v 1.8 2006/11/21 22:48:33 momjian Exp $ --> <!-- $PostgreSQL: pgsql/doc/src/sgml/high-availability.sgml,v 1.9 2006/11/22 03:44:52 momjian Exp $ -->
<chapter id="high-availability"> <chapter id="high-availability">
<title>High Availability and Load Balancing</title> <title>High Availability and Load Balancing</title>
...@@ -193,11 +193,13 @@ protocol to make nodes agree on a serializable transactional order. ...@@ -193,11 +193,13 @@ protocol to make nodes agree on a serializable transactional order.
other server before each transaction commits. Heavy write other server before each transaction commits. Heavy write
activity can cause excessive locking, leading to poor performance. activity can cause excessive locking, leading to poor performance.
In fact, write performance is often worse than that of a single In fact, write performance is often worse than that of a single
server. Read requests can be sent to any server. Clustering server. Read requests can be sent to any server. Some
is best for mostly read workloads, though its big advantage implementations use cluster-wide shared memory or shared disk
is that any server can accept write requests &mdash; there is to reduce the communication overhead. Clustering is best for
no need to partition workloads between master and slave servers, mostly read workloads, though its big advantage is that any
and because the data changes are sent from one server to another, server can accept write requests &mdash; there is no need to
partition workloads between master and slave servers, and
because the data changes are sent from one server to another,
there is no problem with non-deterministic functions like there is no problem with non-deterministic functions like
<function>random()</>. <function>random()</>.
</para> </para>
......
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