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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 <productname>PostgreSQL</> periodically writes full page images to
permanent WAL storage <emphasis>before</> modifying the actual page on permanent WAL storage <emphasis>before</> modifying the actual page on
disk. By doing this, during crash recovery <productname>PostgreSQL</> can disk. By doing this, during crash recovery <productname>PostgreSQL</> can
restore partially-written pages from WAL. If you have a battery-backed disk restore partially-written pages from WAL. If you have file-system software
controller or file-system software that prevents partial page writes that prevents partial page writes (e.g., ZFS), you can turn off
(e.g., ZFS), you can safely turn off this page imaging by turning off the this page imaging by turning off the <xref
<xref linkend="guc-full-page-writes"> parameter. 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> </para>
</sect1> </sect1>