Turning off atime on PostgreSQL DB volumes

From: "Keaton Adams" <kadams(at)mxlogic(dot)com>
To: <pgsql-general(at)postgresql(dot)org>
Subject: Turning off atime on PostgreSQL DB volumes
Date: 2007-08-28 14:07:12
Message-ID: 0B34A6972BF39E4CB465A64DBBAD2BB9023ACEEC@mxlhq-exch01.corp.mxlogic.com
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After reading several articles on the performance drag that Linux atime
has on file systems we would like to mount our DB volumes with the
noatime parameter to see just what type of a performance gain we will
achieve. Does PostgreSQL use atime in any way when reading/writing
data? If we turn off/disable atime on the DB volumes will that cause
any type of issue at all with PostgreSQL 8.1 on Red Hat Enterprise
Linux?

Ingo Molnar who is the real-time/performance guru of the Linux Kernel
wrote "I cannot over-emphasize how much of a deal it is in practice.
Atime updates are by far the biggest IO performance deficiency that
Linux has today. Getting rid of atime updates would give us more
everyday Linux performance than all the page cache speedups of the past
10 years, _combined_".

The atime is updated (synchronously) for queries as well as
updates/inserts whereas logs/journals are only updated (synchronously)
for the updates/inserts... This is true for every read -- even if it is
page by page -- each page request causes a synchronous atime update.

http://kerneltrap.org/node/14148

Thanks,

Keaton

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