From f3224e010dbd372a5411c5ddf0aae27f35007b65 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Wed, 8 Dec 2010 20:01:19 -0500 Subject: Force default wal_sync_method to be fdatasync on Linux. Recent versions of the Linux system header files cause xlogdefs.h to believe that open_datasync should be the default sync method, whereas formerly fdatasync was the default on Linux. open_datasync is a bad choice, first because it doesn't actually outperform fdatasync (in fact the reverse), and second because we try to use O_DIRECT with it, causing failures on certain filesystems (e.g., ext4 with data=journal option). This part of the patch is largely per a proposal from Marti Raudsepp. More extensive changes are likely to follow in HEAD, but this is as much change as we want to back-patch. Also clean up confusing code and incorrect documentation surrounding the fsync_writethrough option. Those changes shouldn't result in any actual behavioral change, but I chose to back-patch them anyway to keep the branches looking similar in this area. In 9.0 and HEAD, also do some copy-editing on the WAL Reliability documentation section. Back-patch to all supported branches, since any of them might get used on modern Linux versions. --- doc/src/sgml/config.sgml | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-) (limited to 'doc/src') diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index 3aa74870f88..f3287219627 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -1442,12 +1442,12 @@ SET ENABLE_SEQSCAN TO OFF; - fsync_writethrough (call fsync() at each commit, forcing write-through of any disk write cache) + fsync (call fsync() at each commit) - fsync (call fsync() at each commit) + fsync_writethrough (call fsync() at each commit, forcing write-through of any disk write cache) @@ -1457,12 +1457,11 @@ SET ENABLE_SEQSCAN TO OFF; - Not all of these choices are available on all platforms. The open_* options also use O_DIRECT if available. + 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. - The default is the first method in the above list that is supported - by the platform. The default is not necessarily ideal; it might be + by the platform, except that fdatasync is the default on + Linux. The default is not necessarily ideal; it might be necessary to change this setting or other aspects of your system configuration in order to create a crash-safe configuration or achieve optimal performance. -- cgit v1.2.3