diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index affce37d0d..87d182c4c4 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -1570,7 +1570,11 @@ SET ENABLE_SEQSCAN TO OFF;
Not all of these choices are available on all platforms.
The default is the first method in the above list that is supported
- by the platform.
+ by the platform. The default is not necessarily best; it may be
+ necessary to change this setting, or other aspects of your system
+ configuration, in order to create a crash-safe configuration, as
+ discussed in , or to achieve best
+ performance.
The open_>* options also use O_DIRECT> if available.
The utility src/tools/fsync> in the PostgreSQL source tree
can do performance testing of various fsync methods.
diff --git a/doc/src/sgml/wal.sgml b/doc/src/sgml/wal.sgml
index 6730c9328e..2726acb8a7 100644
--- a/doc/src/sgml/wal.sgml
+++ b/doc/src/sgml/wal.sgml
@@ -85,7 +85,9 @@
by unchecking My Computer\Open\{select disk
drive}\Properties\Hardware\Properties\Policies\Enable write caching on
the disk>. Also on Windows, fsync> and
- fsync_writethrough> never do write caching.
+ fsync_writethrough> never do write caching. The
+ fsync_writethrough> option can also be used to disable
+ write caching on MacOS X>.
@@ -529,8 +531,10 @@
The parameter determines how
PostgreSQL will ask the kernel to force
WAL updates out to disk.
- All the options should be the same in terms of reliability,
- but it's quite platform-specific which one will be the fastest.
+ With the exception of fsync_writethrough>, which can sometimes
+ force a flush of the disk cache even when other options do not do so,
+ all the options should be the same in terms of reliability.
+ However, it's quite platform-specific which one will be the fastest.
Note that this parameter is irrelevant if fsync
has been turned off.
@@ -590,6 +594,7 @@
irrecoverable data corruption. Administrators should try to ensure
that disks holding PostgreSQL's
WAL log files do not make such false reports.
+ (See .)