Message-ID: <4C3532CC.6070601@squeakycode.net>
Date: Wed, 07 Jul 2010 21:07:08 -0500
From: Andy Colson <andy@squeakycode.net>
User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US;
	rv:1.9.2.4) Gecko/20100608 Lightning/1.0b2 Thunderbird/3.1
MIME-Version: 1.0
To: Ryan Wexler <ryan@iridiumsuite.com>,
 pgsql-performance@postgresql.org
Subject: Re: performance on new linux box
References: <AANLkTinVrej5r_uF3As3mF8BW4CYgLGiw2-v2HORsqjM@mail.gmail.com>
In-Reply-To: <AANLkTinVrej5r_uF3As3mF8BW4CYgLGiw2-v2HORsqjM@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit

On 07/07/2010 06:06 PM, Ryan Wexler wrote:
> Postgresql was previously running on a single cpu linux machine with 2 gigs of memory and a single sata drive (v8.3).  Basically a desktop with linux on it.  I experienced slow performance.
>
> So, I finally moved it to a real server.  A dually zeon centos machine with 6 gigs of memory and raid 10, postgres 8.4.  But, I am now experiencing even worse performance issues.
>
> My system is consistently highly transactional.  However, there is also regular complex queries and occasional bulk loads.
>
> On the new system the bulk loads are extremely slower than on the previous machine and so are the more complex queries.  The smaller transactional queries seem comparable but i had expected an improvement.  Performing a db import via psql -d databas -f dbfile illustrates this problem.  It takes 5 hours to run this import.  By contrast, if I perform this same exact import on my crappy windows box with only 2 gigs of memory and default postgres settings it takes 1 hour.  Same deal with the old linux machine.  How is this possible?
>
> Here are some of my key config settings:
> max_connections = 100
> shared_buffers = 768MB
> effective_cache_size = 2560MB
> work_mem = 16MB
> maintenance_work_mem = 128MB
> checkpoint_segments = 7
> checkpoint_timeout = 7min
> checkpoint_completion_target = 0.5
>
> I have tried varying the shared_buffers size from 128 all the way to 1500mbs and got basically the same result.   Is there a setting change I should be considering?
>
> Does 8.4 have performance problems or is this unique to me?
>
> thanks
>

Yeah, I inherited a "server" (the quotes are sarcastic air quotes), with really bad disk IO... er.. really safe disk IO.  Try the dd test.  On my desktop I get 60-70 meg a second.  On this "server" (I laugh) I got about 20.  I had to go out of my way (way out) to enable the disk caching, and even then only got 50 meg a second.

http://www.westnet.com/~gsmith/content/postgresql/pg-disktesting.htm

-Andy