From 7a1ca8977fd109a86b540444f71f24bd2f38ea43 Mon Sep 17 00:00:00 2001 From: Bruce Momjian Date: Wed, 22 Dec 2010 21:12:00 -0500 Subject: [PATCH] Document that BBU's do not allow partial page writes to be safely turned off unless they guarantee that all writes to the BBU arrive in 8kB chunks. Per discussion with Greg Smith --- doc/src/sgml/wal.sgml | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/doc/src/sgml/wal.sgml b/doc/src/sgml/wal.sgml index b44a6257ec..10ce786f15 100644 --- a/doc/src/sgml/wal.sgml +++ b/doc/src/sgml/wal.sgml @@ -167,10 +167,12 @@ PostgreSQL periodically writes full page images to permanent WAL storage before modifying the actual page on disk. By doing this, during crash recovery 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 - 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 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. -- 2.40.0