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<chapter id="wal">

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

write caching. On <productname>FreeBSD</> use

<application>atacontrol</>. (For SCSI disks use <ulink

url="http://sg.torque.net/sg/sdparm.html"><application>sdparm</></ulink>

to turn off <literal>WCE</>.) On <productname>Windows</> if

<varname>wal_sync_method</> is <literal>open_datasync</> (the default),

write caching is disabled by unchecking <literal>My

Computer\Open\{select disk

to turn off <literal>WCE</>.) On <productname>Solaris</> the disk

write cache is controlled by <ulink

url="http://www.sun.com/bigadmin/content/submitted/format_utility.jsp"><literal>format

-e</></ulink>. (The Solaris <acronym>ZFS</> file system is safe with

disk write-cache enabled because it issues its own disk cache flush

commands.) On <productname>Windows</> if <varname>wal_sync_method</>

is <literal>open_datasync</> (the default), write caching is disabled

by unchecking <literal>My Computer\Open\{select disk

drive}\Properties\Hardware\Properties\Policies\Enable write caching on

the disk</>. Also on Windows, <literal>fsync</> and

<literal>fsync_writethrough</> never do write caching.