|From:||Joshua Drake <jd(at)commandprompt(dot)com>|
|To:||"Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>|
|Cc:||"Josh Berkus" <josh(at)agliodbs(dot)com>, "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "Alvaro Herrera" <alvherre(at)commandprompt(dot)com>, "Hans-Juergen Schoenig" <postgres(at)cybertec(dot)at>, "Peter Eisentraut" <peter_e(at)gmx(dot)net>, "Magnus Hagander" <magnus(at)hagander(dot)net>, <pgsql-hackers(at)postgresql(dot)org>|
|Subject:||Re: A smaller default postgresql.conf|
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On Tue, 19 Aug 2008 12:17:46 -0500
"Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov> wrote:
> Well, this sure looks scary:
> # maintenance_work_mem = 256MB #webserver with 2GB RAM
I would agree. 2GB isn't that much memory as it is and that is a fairly
heft amount of maintenance_work_mem. This isn't the days when vacuum
ran via cron at 2am anymore. Autovacuum will fire at any time.
> But I'm amazed by this, too:
> # max_connections = 700 # web application database
> How many CPUs and spindles are you assuming there?
> My testing and experience suggest applications should use no more than
> 4 per CPU plus 2 per spindle, absolute maximum. Don't you find that a
> connection pool with queuing capability is required for best
> performance with a large number of users?
I just did the math on this and I would say you are correct. I had
never really evaluated in the way you just had but based on some of our
larger installs (32cores, 100 spindles) your math works.
Noting that he actually states it is a webserver connecting there
should absolutely be a pool in front of PostgreSQL.
Joshua D. Drake
The PostgreSQL Company since 1997: http://www.commandprompt.com/
PostgreSQL Community Conference: http://www.postgresqlconference.org/
United States PostgreSQL Association: http://www.postgresql.us/
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