diff options
| -rw-r--r-- | doc/src/sgml/config.sgml | 6 | ||||
| -rw-r--r-- | doc/src/sgml/wal.sgml | 11 |
2 files changed, 13 insertions, 4 deletions
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index 39be6243cac..b904238800a 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -1570,7 +1570,11 @@ SET ENABLE_SEQSCAN TO OFF; <para> 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 <xref linkend="wal-reliability">, or to achieve best + performance. 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. diff --git a/doc/src/sgml/wal.sgml b/doc/src/sgml/wal.sgml index 8a118cfece8..70fc832e23d 100644 --- a/doc/src/sgml/wal.sgml +++ b/doc/src/sgml/wal.sgml @@ -85,7 +85,9 @@ 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. + <literal>fsync_writethrough</> never do write caching. The + <literal>fsync_writethrough</> option can also be used to disable + write caching on <productname>MacOS X</>. </para> <para> @@ -529,8 +531,10 @@ The <xref linkend="guc-wal-sync-method"> parameter determines how <productname>PostgreSQL</productname> will ask the kernel to force <acronym>WAL</acronym> 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 <literal>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 <varname>fsync</varname> has been turned off. </para> @@ -590,6 +594,7 @@ irrecoverable data corruption. Administrators should try to ensure that disks holding <productname>PostgreSQL</productname>'s <acronym>WAL</acronym> log files do not make such false reports. + (See <xref linkend="wal-reliability">.) </para> <para> |