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Update file system snapshot docs.

This commit is contained in:
Bruce Momjian 2005-03-17 15:38:46 +00:00
parent 57fdb2b0d8
commit 28d150d8e9
1 changed files with 12 additions and 9 deletions
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21
doc/src/sgml/backup.sgml
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@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/backup.sgml,v 2.58 2005/03/17 05:10:11 momjian Exp $
$PostgreSQL: pgsql/doc/src/sgml/backup.sgml,v 2.59 2005/03/17 15:38:46 momjian Exp $
-->
<chapter id="backup">
<title>Backup and Restore</title>
@ -364,9 +364,11 @@ tar -cf backup.tar /usr/local/pgsql/data
</para>
<para>
If your database is spread across multiple volumes (for example,
if you are using tablespaces) there may not be any way
to obtain exactly-simultaneous frozen snapshots of all the volumes.
If your database is spread across multiple file systems there may not
be any way to obtain exactly-simultaneous frozen snapshots of all
the volumes. For example, if your data files and WAL log on different
file disks, or if tablespaces are on different file systems, it might
not be possible to use snapshots because the snapshots must be simultaneous.
Read your file system documentation very carefully before trusting
to the consistent-snapshot technique in such situations. The safest
approach is to shut down the database server for long enough to
@ -375,11 +377,12 @@ tar -cf backup.tar /usr/local/pgsql/data
<para>
Another option is to use <application>rsync</> to perform a file
system backup. First, while the database server is running,
run <application>rsync</>, then shut down the database
server and perform a second <application>rsync</>, then
restart the database server. This allows a file system backup to be
performed with minimal downtime.
system backup. This is done by first running <application>rsync</>
while the database server is running, then shutting down the database
server just long enough to do a second <application>rsync</>. The
second <application>rsync</> will be much quicker than the first,
but will be consistent because the server was down. This method
allows a file system backup to be performed with minimal downtime.
</para>
<para>