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Backpatch to 9.0 a doc mention that a BBU does not prevent partial page

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writes.
This commit is contained in:
Bruce Momjian
2010-12-24 11:32:52 -05:00
parent 554b00cdab
commit c474585295
1 changed files with 6 additions and 4 deletions
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10
doc/src/sgml/wal.sgml
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@ -167,10 +167,12 @@
<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>