Re: Configuration for a new server.

From: "Benjamin Krajmalnik" <kraj(at)servoyant(dot)com>
To: "Greg Smith" <greg(at)2ndquadrant(dot)com>
Cc: <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Configuration for a new server.
Date: 2011-02-02 17:46:06
Message-ID: F4E6A2751A2823418A21D4A160B689887B0E51@fletch.stackdump.local
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>See how buffers_backend is much larger than buffers_clean, even though maxwritten_clean is low?  That means the background writer isn't running often enough to keep up with cleaning things, even though >it does a lot of work when it does kick in.  In your situation I'd normally do a first pass by cutting bgwriter_lru_maxpages to 1/4 of what it is now, cut bgwriter_delay to 1/4 as well (to 50ms), and >then see how the proportions change.  You can probably cut the multiplier, too, yet still see more pages written by the cleaner.

>I recommend saving a snapsot of this data with a timestamp, i.e.:

>select now(),* from pg_stat_bgwriter;

>Anytime you make a change to one of the background writer or checkpoint timing parameters.  That way you have a new baseline to compare against.  These numbers aren't very useful with a single value, >but once you get two of them with timestamps you can compute all sorts of fun statistics from the pair.

So, if I understand correctly, I should strive for a relative increase in buffers_clean to buffers_backend

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