Subject: Re: How to get higher tps
From: Jeff Davis <pgsql@j-davis.com>
To: Marty Jia <mjia@ask.com>
Cc: pgsql-performance@postgresql.org
In-Reply-To: 
 <0B9A8C89DCC3AB488A78A4DE0FECDA90019E30D4@SITE3MAIL04.jeeves.ask.info>
References: 
 <0B9A8C89DCC3AB488A78A4DE0FECDA90019E30D4@SITE3MAIL04.jeeves.ask.info>
Content-Type: text/plain
Date: Mon, 21 Aug 2006 14:23:26 -0700
Message-Id: <1156195406.15743.28.camel@dogma.v10.wvs>
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit

On Mon, 2006-08-21 at 16:45 -0400, Marty Jia wrote:
> I'm exhausted to try all performance tuning ideas, like following
> parameters
> 
> shared_buffers 
> fsync 

By "tuning" fsync, what do you mean? Did you turn it off?

If you turned fsync off, that could compromise your data in case of any
kind of crash or power failure. However, if you turn fsync off you
should much higher TPS on pgbench than you're getting.


> Dual Intel Xeon 2.8GHz
> 6GB RAM
> Linux 2.4 kernel
> RedHat Enterprise Linux AS 3
> 200GB for PGDATA on 3Par, ext3
> 50GB for WAL on 3Par, ext3

Does your disk controller have battery-backed writeback cache? How much?

> With PostgreSql 8.1.4
> 
> We don't have i/o bottle neck. 
> 

Well, chances are PostgreSQL is waiting for fsync, which means you do
have an I/O bottleneck (however, you're not using all of your I/O
bandwidth, most likely).

Regards,
	Jeff Davis