<!-- doc/src/sgml/pgtestfsync.sgml -->

<sect1 id="pgtestfsync">
 <title>pg_test_fsync</title>

 <indexterm zone="pgtestfsync">
  <primary>pg_test_fsync</primary>
 </indexterm>

 <para>
  <application>pg_test_fsync</> is intended to give you a reasonable
  idea of what the fastest <xref linkend="guc-wal-sync-method"> is on your
  specific system,
  as well as supplying diagnostic information in the event of an
  identified I/O problem.  However, differences shown by pg_test_fsync
  might not make any difference in real database throughput, especially
  since many database servers are not speed-limited by their transaction
  logs.
 </para>

 <sect2>
  <title>Usage</title>

<synopsis>
pg_test_fsync [options]
</synopsis>

   <para>
    <application>pg_test_fsync</application> accepts the following
    command-line options:

    <variablelist>

     <varlistentry>
      <term><option>-f</option></term>
      <term><option>--filename</option></term>
      <listitem>
       <para>
        Specifies the filename to write test data in.
        This file should be in the same file system that the
        <filename>pg_xlog</> directory is or will be placed in.
        (<filename>pg_xlog</> contains the <acronym>WAL</> files.)
        The default is <filename>pg_test_fsync.out</> in the current
        directory.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-o</option></term>
      <term><option>--ops-per-test</option></term>
      <listitem>
       <para>
        Specifies the number of operations per test.  The more operations
        per test, the greater the test's accuracy, but the longer it takes
        to run.  The default is 2000.
       </para>
      </listitem>
     </varlistentry>

    </variablelist>
   </para>

 </sect2>

 <sect2>
  <title>Author</title>

  <para>
   Bruce Momjian <email>bruce@momjian.us</email>
  </para>
 </sect2>

</sect1>
