User-Agent: Microsoft-Entourage/11.2.1.051004
Date: Fri, 24 Feb 2006 22:22:49 -0800
Subject: Re: Reliability recommendations
From: "Luke Lonergan" <llonergan@greenplum.com>
To: "Mark Kirkwood" <markir@paradise.net.nz>
cc: "Dan Gorman" <dgorman@hi5.com>, "Joshua D. Drake" <jd@commandprompt.com>,
	"Craig A. James" <cjames@modgraph-usa.com>,
	pgsql-performance@postgresql.org
Message-ID: <C02537B9.1DC8D%llonergan@greenplum.com>
Thread-Topic: [PERFORM] Reliability recommendations
Thread-Index: AcY50+Y4JREnwqXHEdqbDgANk63kWA==
In-Reply-To: <43FFF4EF.6060601@paradise.net.nz>
MIME-Version: 1.0
Content-Type: text/plain;
 charset=us-ascii
Content-Transfer-Encoding: 7bit

Mark,

On 2/24/06 10:10 PM, "Mark Kirkwood" <markir@paradise.net.nz> wrote:

> Well, since this is always fun (2G memory, 3Ware 7506, 4xPATA), writing:
> 
> $ dd if=/dev/zero of=/data0/dump/bigfile bs=8k count=500000
> 500000 records in
> 500000 records out
> 4096000000 bytes transferred in 32.619208 secs (125570185 bytes/sec)

> Reading:
> 
> $ dd of=/dev/null if=/data0/dump/bigfile bs=8k count=500000
> 500000 records in
> 500000 records out
> 4096000000 bytes transferred in 24.067298 secs (170189442 bytes/sec)

Not bad at all!  I have one of these cards in my home machine running WinXP
and it's not nearly this fast.
 
> Hmmm - a bit humbled by Luke's machinery :-), however, mine is probably
> competitive on (MB/s)/$....

Not sure - the machines I cite are about $10K each.  The machine you tested
was probably about $1500 a few years ago (my guess), and with a 5:1 ratio in
speed versus about a 6:1 ratio in price, we're not too far off in MB/s/$
after all :-)
 
> It would be interesting to see what Dan's system would do on a purely
> sequential workload - as 40-50MB of purely random IO is high.

Yeah - that is really high if the I/O is really random.  I'd normally expect
maybe 500-600 iops / second and if each IO is 8KB, that would be 4MB/s.  The
I/O is probably not really completely random, or it's random over cachable
bits of the occupied disk area.

- Luke