index 54fcf93954da608e6e9651882a58aebc8b673ab5..e212ddf16c032ccb22da12337b3ffb96665aeb08 100644 (file)
<productname>PostgreSQL</> periodically writes full page images to
permanent WAL storage <emphasis>before</> modifying the actual page on
disk. By doing this, during crash recovery <productname>PostgreSQL</> can
- restore partially-written pages from WAL. If you have a battery-backed disk
- controller or file-system software that prevents partial page writes
- (e.g., ZFS), you can safely turn off this page imaging by turning off the
- <xref linkend="guc-full-page-writes"> parameter.
+ restore partially-written pages from WAL. If you have file-system software
+ that prevents partial page writes (e.g., ZFS), you can turn off
+ this page imaging by turning off the <xref
+ linkend="guc-full-page-writes"> parameter. Battery-Backed Unit
+ (BBU) disk controllers do not prevent partial page writes unless
+ they guarantee that data is written to the BBU as full (8kB) pages.
</para>
</sect1>