Clarify replication items, and define some terms.
This commit is contained in:
parent
e05a3c30b0
commit
c7a6046a59
|
@ -1,4 +1,4 @@
|
||||||
<!-- $PostgreSQL: pgsql/doc/src/sgml/failover.sgml,v 1.6 2006/11/15 01:09:08 momjian Exp $ -->
|
<!-- $PostgreSQL: pgsql/doc/src/sgml/failover.sgml,v 1.7 2006/11/16 18:25:58 momjian Exp $ -->
|
||||||
|
|
||||||
<chapter id="failover">
|
<chapter id="failover">
|
||||||
<title>Failover, Replication, Load Balancing, and Clustering Options</title>
|
<title>Failover, Replication, Load Balancing, and Clustering Options</title>
|
||||||
|
@ -32,6 +32,18 @@
|
||||||
minimizes its impact for a specific workload.
|
minimizes its impact for a specific workload.
|
||||||
</para>
|
</para>
|
||||||
|
|
||||||
|
<para>
|
||||||
|
Some solutions deal with synchronization by allowing only one
|
||||||
|
server to modify the data. Servers that can modify data are
|
||||||
|
called read/write or "master" server. Servers with read-only
|
||||||
|
data are called backup or "slave" servers. As you will see below,
|
||||||
|
these terms cover a variety of implementations. Some servers
|
||||||
|
are masters of some data sets, and slave of others. Some slaves
|
||||||
|
cannot be accessed until they are changed to master servers,
|
||||||
|
while other slaves can reply to read-only queries while they are
|
||||||
|
slaves.
|
||||||
|
</para>
|
||||||
|
|
||||||
<para>
|
<para>
|
||||||
Some failover and load balancing solutions are synchronous, meaning that
|
Some failover and load balancing solutions are synchronous, meaning that
|
||||||
a data-modifying transaction is not considered committed until all
|
a data-modifying transaction is not considered committed until all
|
||||||
|
@ -118,15 +130,20 @@
|
||||||
<title>Data Partitioning</title>
|
<title>Data Partitioning</title>
|
||||||
|
|
||||||
<para>
|
<para>
|
||||||
Data partitioning splits tables into data sets. Each set can only be
|
Data partitioning splits tables into data sets. Each set can
|
||||||
modified by one server. For example, data can be partitioned by
|
be modified by only one server. For example, data can be
|
||||||
offices, e.g. London and Paris. While London and Paris servers have all
|
partitioned by offices, e.g. London and Paris. While London
|
||||||
data records, only London can modify London records, and Paris can only
|
and Paris servers have all data records, only London can modify
|
||||||
modify Paris records.
|
London records, and Paris can only modify Paris records. This
|
||||||
|
is similar to section <xref
|
||||||
|
linkend="continuously-running-replication-server"> above, except
|
||||||
|
that instead of having a read/write server and a read-only server,
|
||||||
|
each server has a read/write data set and a read-only data
|
||||||
|
set.
|
||||||
</para>
|
</para>
|
||||||
|
|
||||||
<para>
|
<para>
|
||||||
Such partitioning implements both failover and load balancing. Failover
|
Such partitioning provides both failover and load balancing. Failover
|
||||||
is achieved because the data resides on both servers, and this is an
|
is achieved because the data resides on both servers, and this is an
|
||||||
ideal way to enable failover if the servers share a slow communication
|
ideal way to enable failover if the servers share a slow communication
|
||||||
channel. Load balancing is possible because read requests can go to any
|
channel. Load balancing is possible because read requests can go to any
|
||||||
|
|
Loading…
Reference in New Issue