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Re: how much postgres can scale up?

From: "Anibal David Acosta" <aa(at)devshock(dot)com>
To: <tv(at)fuzzy(dot)cz>
Cc: <pgsql-performance(at)postgresql(dot)org>
Subject: Re: how much postgres can scale up?
Date: 2011-06-10 12:56:50
Message-ID: 000f01cc276d$df82edc0$9e88c940$@devshock.com (view raw or flat)
Thread:
Lists: pgsql-performance
The version is Postgres 9.0
Yes, I setup the postgres.conf according to instructions in the 
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?

Thanks!


-----Mensaje original-----
De: tv(at)fuzzy(dot)cz [mailto:tv(at)fuzzy(dot)cz] 
Enviado el: viernes, 10 de junio de 2011 08:10 a.m.
Para: Anibal David Acosta
CC: pgsql-performance(at)postgresql(dot)org
Asunto: Re: [PERFORM] how much postgres can scale up?

> I have a function in pgsql language, this function do some select to 
> some tables for verify some conditions and then do one insert to a 
> table with NO index. Update are not performed in the function
>
> When 1 client connected postgres do 180 execution per second With 2 
> clients connected postgres do 110 execution per second With 3 clients 
> connected postgres do 90 execution per second
>
> Finally with 6 connected clients postgres do 60 executions per second 
> (totally 360 executions per second)
>
> While testing, I monitor disk, memory and CPU and not found any overload.

There's always a bottleneck - otherwise the system might run faster (and hit another bottleneck eventually). It might be CPU, I/O, memory, locking and maybe some less frequent things.

> I know that with this information you can figure out somethigns, but 
> in normal conditions, Is normal the degradation of performance per 
> connection when connections are incremented?
> Or should I spect 180 in the first and something similar in the second 
> connection? Maybe 170?
>
>
> The server is a dual xeon quad core with 16 GB of ram and a very fast 
> storage The OS is a windows 2008 R2 x64

Might be, but we need more details about how the system works. On Linux I'd ask for output from 'iostat -x 1' and 'vmstat 1' but you're on Windows so there are probably other tools.

What version of PostgreSQL is this? What are the basic config values (shared_buffers, work_mem, effective_cache_size, ...)? Have you done some tuning? There's a wiki page about this:
http://wiki.postgresql.org/wiki/Tuning_Your_PostgreSQL_Server

Have you tried to log slow queries? Maybe there's one query that makes the whole workload slow? See this:
http://wiki.postgresql.org/wiki/Logging_Difficult_Queries

Tomas


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