fsync test tools

Add link to exteran fsync testing script and our fsync test tool.

doc/src/sgml/config.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.233 2009/11/13 22:43:39 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.234 2009/11/28 16:21:31 momjian Exp $ -->
 
 <chapter Id="runtime-config">
   <title>Server Configuration</title>
@@ -1432,6 +1432,8 @@ SET ENABLE_SEQSCAN TO OFF;
         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>

doc/src/sgml/wal.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/wal.sgml,v 1.59 2009/04/09 16:20:50 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/wal.sgml,v 1.60 2009/11/28 16:21:31 momjian Exp $ -->
 
 <chapter id="wal">
  <title>Reliability and the Write-Ahead Log</title>
@@ -86,6 +86,8 @@
    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>