From: "Dave Page" <dpage@vale-housing.co.uk>
To: <llonergan@greenplum.com>,
	<kenjim@juniper.net>,
	<kometen@gmail.com>
Cc: <pgsql-performance@postgresql.org>
Subject: Re: Best OS & Configuration for Dual Xeon w/4GB &
Message-ID: <008b01c64b81$b737fcb0$6a01a8c0@valehousing.co.uk>
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	charset="utf-8"
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Date: Sun, 19 Mar 2006 18:19:40 -0000
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Thread-Topic: [PERFORM] Best OS & Configuration for Dual Xeon w/4GB &
thread-index: AcZKIDwQk+uFjzHfRo2txPlZ02oXPABasGbcAAJRnDo=


-----Original Message-----
From: "Luke Lonergan"<llonergan@greenplum.com>
Sent: 19/03/06 16:26:58
To: "Kenji Morishige"<kenjim@juniper.net>, "Claus =
Guttesen"<kometen@gmail.com>
Cc: "pgsql-performance@postgresql.org"<pgsql-performance@postgresql.org>
Subject: Re: [PERFORM] Best OS & Configuration for Dual Xeon w/4GB &

> I notice that no one asked you about your disk bandwidth - the Adaptec =
2200S
>is a "known bad" controller -=20

Agreed - We have a couple at work which got relagated to use in 'toy' =
boxes when we realised how bad they were, long before they ever saw any =
production use.

Regards, Dave

-----Unmodified Original Message-----
Kenji,


On 3/17/06 4:08 PM, "Kenji Morishige" <kenjim@juniper.net> wrote:

> Thanks guys, I'm studying each of your responses and am going to start =
to
> experiement.

I notice that no one asked you about your disk bandwidth - the Adaptec =
2200S
is a "known bad" controller - the bandwidth to/from in RAID5 is about =
1/2 to
1/3 of a single disk drive, which is far too slow for a 10GB database, =
and
IMO should disqualify a RAID adapter from being used at all.

Without fixing this, I'd suggest that all of the other tuning described =
here
will have little value, provided your working set is larger than your =
RAM.

You should test the I/O bandwidth using these simple tests:
  time bash -c "dd if=3D/dev/zero of=3Dbigfile bs=3D8k count=3D1000000 =
&& sync"

then:
  time dd if=3Dbigfile of=3D/dev/null bs=3D8k

You should get on the order of 150MB/s on four disk drives in RAID5.

And before people jump in about "random I/O", etc, the sequential scan =
test
will show whether the controller is just plain bad very quickly.  If it
can't do sequential fast, it won't do seeks fast either.

- Luke


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