Document that non-data journaling is a recommended mount option.

diff --git a/doc/src/sgml/wal.sgml b/doc/src/sgml/wal.sgml
index 373aa961dc7703ccb5f0d39886cc6260b8d4e17d..3b013746a313306c2f0b3f8ba711fd47e7f3c35f 100644 (file)
--- a/doc/src/sgml/wal.sgml
+++ b/doc/src/sgml/wal.sgml
@@ -1,4 +1,4 @@
-
+
 
 
  Reliability and the Write-Ahead Log
@@ -135,6 +135,21 @@
     roll-forward recovery, also known as REDO.)
    
 
+   
+    
+     Because WAL restores database file
+     contents after a crash, it is not necessary to use a
+     journaled filesystem;  in fact, journaling overhead can
+     reduce performance.  For best performance, turn off
+     data journaling as a filesystem mount
+     option, e.g. use data=writeback on Linux.
+     Meta-data journaling (e.g.  file creation and directory
+     modification) is still desirable for faster rebooting after
+     a crash.
+    
+   
+
+
    
     Using WAL results in a
     significantly reduced number of disk writes, because only the log