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Re: New to PostgreSQL, performance considerations

From: Greg Smith <gsmith(at)gregsmith(dot)com>
To: Postgresql Performance list <pgsql-performance(at)postgresql(dot)org>
Subject: Re: New to PostgreSQL, performance considerations
Date: 2006-12-14 15:00:14
Message-ID: Pine.GSO.4.64.0612140950460.11833@westnet.com (view raw or flat)
Thread:
Lists: pgsql-performance
On Wed, 13 Dec 2006, Ron wrote:

> The slowest results, Michael's, are on the system with what appears to be the 
> slowest CPU of the bunch; and the ranking of the rest of the results seem to 
> similarly depend on relative CPU performance.  This is not what one would 
> naively expect when benching a IO intensive app like a DBMS.

pgbench with 3000 total transactions and fsync off is barely doing I/O to 
disk; it's writing a bunch of data to the filesystem cache and ending the 
benchmark before the data even makes it to the hard drive.  This is why 
his results become completely different as soon as the number of 
transactions increases. With little or no actual disk writes, you should 
expect results to be ranked by CPU speed.

--
* Greg Smith gsmith(at)gregsmith(dot)com http://www.gregsmith.com Baltimore, MD

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