From: Andy Colson <andy@squeakycode.net>
To: Michael Kohl <michael.kohl@tupalo.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: High load,
Date: Thu, 27 Jan 2011 09:06:38 -0600
Message-ID: <4D4189FE.7080608@squeakycode.net> (raw)
In-Reply-To: <AANLkTikBFzUKmWcVBz_5GQZeQOWtj7Kfeov=M9TWBOJf@mail.gmail.com>
References: <AANLkTikBFzUKmWcVBz_5GQZeQOWtj7Kfeov=M9TWBOJf@mail.gmail.com>
On 1/27/2011 4:31 AM, Michael Kohl wrote:
> Hi all,
>
> we are running a fairly big Ruby on Rails application on Postgres 8.4.
> Our traffic grew quite a bit lately, and since then we are facing DB
> performance issues. System load occasionally explodes (around 170
> yesterday on a 16 core system), which seems to be caused by disk I/O
> (iowait in our Munin graphs goes up significantly during these
> periods). At other times the laod stays rather low under pretty much
> the same circumstances.
>
> There are 6 application servers with 18 unicorns each, as well as 12
> beanstalk workers talking to the DB. I know the problem description is
> very vague, but so far we haven't consistently managed to reproduce
> the problem. Turning of the beanstalk workers usually leads to a great
> decreases in writes and system loads, but during yesterday's debugging
> session they obviously ran fine (thanks, Murphy).
>
> Below you'll find our system information and Postgres config, maybe
> someone could be so kind as to point out any obvious flaws in our
> current configuration while I'm trying to get a better description of
> the underlying problem.
>
<SNIP>
If the suggestions below are not enough, you might have to check some of
your sql statements and make sure they are all behaving. You may not
notice a table scan when the user count is low, but you will when it
gets higher.
Have you run each of your queries through explain analyze lately?
Have you checked for bloat?
You are vacuuming/autovacuuming, correct?
-Andy
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To: pgsql-performance@postgresql.org
Cc: andy@squeakycode.net, michael.kohl@tupalo.com
Subject: Re: High load,
In-Reply-To: <4D4189FE.7080608@squeakycode.net>
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