-<!-- $PostgreSQL: pgsql/doc/src/sgml/wal.sgml,v 1.55 2008/12/10 11:05:49 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/wal.sgml,v 1.56 2008/12/18 22:21:16 momjian Exp $ -->
<chapter id="wal">
<title>Reliability and the Write-Ahead Log</title>
<tip>
<para>
Because <acronym>WAL</acronym> restores database file
- contents after a crash, it is not necessary to use a
- journaled filesystem for reliability. In fact, journaling
+ contents after a crash, journaled filesystems are necessary for
+ reliable storage of the data files or WAL files. In fact, journaling
overhead can reduce performance, especially if journaling
causes file system <emphasis>data</emphasis> to be flushed
to disk. Fortunately, data flushing during journaling can