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From: Andres Freund <andres@2ndquadrant.com>
To: ik@postgresql-consulting.com
Cc: Scott Marlowe <scott.marlowe@gmail.com>
Cc: Robert Kaye <rob@musicbrainz.org>
Cc: Josh Krupka <jkrupka@gmail.com>
Cc: PostgreSQL Performance <pgsql-performance@postgresql.org>
Subject: Re: MusicBrainz postgres performance issues
Date: Sun, 15 Mar 2015 18:46:47 +0100
Message-ID: <20150315174646.GH9324@alap3.anarazel.de> (raw)
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On 2015-03-15 20:42:51 +0300, Ilya Kosmodemiansky wrote:
> On Sun, Mar 15, 2015 at 8:20 PM, Andres Freund <andres@2ndquadrant.com> wrote:
> > On 2015-03-15 11:09:34 -0600, Scott Marlowe wrote:
> >> shared_mem of 12G is almost always too large. I'd drop it down to ~1G or so.
> >
> > I think that's a outdated wisdom, i.e. not generally true.
> 
> Quite agreed. With note, that proper configured controller with BBU is needed.

That imo doesn't really have anything to do with it. The primary benefit
of a BBU with writeback caching is accelerating (near-)synchronous
writes. Like the WAL. But, besides influencing the default for
wal_buffers, a larger shared_buffers doesn't change the amount of
synchronous writes.

Greetings,

Andres Freund

-- 
 Andres Freund	                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services


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