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<chapter id="wal">

<title>Reliability and the Write-Ahead Log</title>

<tip>

<para>

Because <acronym>WAL</acronym> restores database file

contents after a crash, journaled filesystems are necessary for

contents after a crash, journaled filesystems arenotnecessary 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