Commit de9ec654 authored by Bruce Momjian's avatar Bruce Momjian

Document that many solid-state drives have volatile write-back caches.

parent 7363021d
<!-- $PostgreSQL: pgsql/doc/src/sgml/wal.sgml,v 1.61 2010/02/03 17:25:06 momjian Exp $ --> <!-- $PostgreSQL: pgsql/doc/src/sgml/wal.sgml,v 1.62 2010/02/20 18:28:37 momjian Exp $ -->
<chapter id="wal"> <chapter id="wal">
<title>Reliability and the Write-Ahead Log</title> <title>Reliability and the Write-Ahead Log</title>
...@@ -59,7 +59,8 @@ ...@@ -59,7 +59,8 @@
same concerns about data loss exist for write-back drive caches as same concerns about data loss exist for write-back drive caches as
exist for disk controller caches. Consumer-grade IDE and SATA drives are exist for disk controller caches. Consumer-grade IDE and SATA drives are
particularly likely to have write-back caches that will not survive a particularly likely to have write-back caches that will not survive a
power failure. To check write caching on <productname>Linux</> use power failure. Many solid-state drives also have volatile write-back
caches. To check write caching on <productname>Linux</> use
<command>hdparm -I</>; it is enabled if there is a <literal>*</> next <command>hdparm -I</>; it is enabled if there is a <literal>*</> next
to <literal>Write cache</>; <command>hdparm -W</> to turn off to <literal>Write cache</>; <command>hdparm -W</> to turn off
write caching. On <productname>FreeBSD</> use write caching. On <productname>FreeBSD</> use
......
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