Date: Thu, 21 Sep 2006 16:49:14 -0500
From: "Jim C. Nasby" <jim@nasby.net>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: yoav x <yoav112003@yahoo.com>, pgsql-performance@postgresql.org
Subject: Re: PostgreSQL and sql-bench
Message-ID: <20060921214913.GV28987@nasby.net>
References: <20060921145244.13005.qmail@web35813.mail.mud.yahoo.com>
	<829.1158851565@sss.pgh.pa.us>
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On Thu, Sep 21, 2006 at 11:12:45AM -0400, Tom Lane wrote:
> yoav x <yoav112003@yahoo.com> writes:
> > I've applied the following parameters to postgres.conf:
> 
> > max_connections = 500
> > shared_buffers = 3000
> > work_mem = 100000
> > effective_cache_size = 3000000000
 
You just told the database that you have 23G of storage.
effective_cache_size is measured in blocks, which are normally 8K.

> Please see my earlier reply --- you ignored at least
> checkpoint_segments, which is critical, and perhaps other things.
> 
> Don't forget also that testing mysql/myisam against fsync = on
> is inherently unfair.

Even with fsync = off, there's still a non-trivial amount of overhead
brought on by MVCC that's missing in myisam. If you don't care about
concurrency or ACIDity, but performance is critical (the case that the
MySQL benchmark favors), then PostgreSQL probably isn't for you.
-- 
Jim Nasby                                            jim@nasby.net
EnterpriseDB      http://enterprisedb.com      512.569.9461 (cell)