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<chapter Id="runtime-config">

<title>Server Configuration</title>

The default is the first method in the above list that is supported

by the platform.

The <literal>open_</>* options also use <literal>O_DIRECT</> if available.

The utility <filename>src/tools/fsync</> in the PostgreSQL source tree

can do performance testing of various fsync methods.

This parameter can only be set in the <filename>postgresql.conf</>

file or on the server command line.

</para>

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<chapter id="wal">

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

ensure data integrity. Avoid disk controllers that have non-battery-backed

write caches. At the drive level, disable write-back caching if the

drive cannot guarantee the data will be written before shutdown.

You can test for reliable I/O subsystem behavior using <ulink

url="http://brad.livejournal.com/2116715.html">diskchecker.pl</ulink>.

</para>

<para>