From: "Anibal David Acosta" <aa@devshock.com>
To: "'Craig Ringer'" <craig@postnewspapers.com.au>
Cc: <tv@fuzzy.cz>,
	<pgsql-performance@postgresql.org>
References: <000601cc2761$a2e3a280$e8aae780$@devshock.com>
	<243bcc276983a6b1e2bbc783c3a5b7db.squirrel@sq.gransy.com>
	<000f01cc276d$df82edc0$9e88c940$@devshock.com>
	<4DF21862.3030008@postnewspapers.com.au>
In-Reply-To: <4DF21862.3030008@postnewspapers.com.au>
Subject: Re: how much postgres can scale up?
Date: Fri, 10 Jun 2011 09:19:22 -0400
Message-ID: <002201cc2771$05531360$0ff93a20$@devshock.com>
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Excellent.

Thanks I'll buy and read that book :)


Thanks!


-----Mensaje original-----
De: Craig Ringer [mailto:craig@postnewspapers.com.au]=20
Enviado el: viernes, 10 de junio de 2011 09:13 a.m.
Para: Anibal David Acosta
CC: tv@fuzzy.cz; pgsql-performance@postgresql.org
Asunto: Re: [PERFORM] how much postgres can scale up?

On 06/10/2011 08:56 PM, Anibal David Acosta wrote:
> The version is Postgres 9.0
> Yes, I setup the postgres.conf according to instructions in the=20
> http://wiki.postgresql.org/wiki/Tuning_Your_PostgreSQL_Server
>
>
> Cool, I will check this
> http://wiki.postgresql.org/wiki/Logging_Difficult_Queries
>
> Looks like great starting point to find bottleneck
>
> But so, Is possible in excellent conditions that two connections =
duplicate the quantity of transactions per second?

For two connections, if you have most of the data cached in RAM or you =
have lots of fast disks, then sure. For that matter, if they're =
synchronized scans of the same table then the second transaction might =
perform even faster than the first one!

There are increasing overheads with transaction synchronization, etc =
with number of connections, and they'll usually land up contending for =
system resources like RAM (for disk cache, work_mem, etc), disk I/O, and =
CPU time. So you won't generally get linear scaling with number of =
connections.

Greg Smith has done some excellent and detailed work on this. I highly =
recommend reading his writing, and you should consider buying his recent =
book "PostgreSQL 9.0 High Performance".

See also:

http://wiki.postgresql.org/wiki/Performance_Optimization

There have been lots of postgresql scaling benchmarks done over time, =
too. You'll find a lot of information if you look around the wiki and =
Google.

--
Craig Ringer