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Date: Wed, 18 Feb 2009 07:42:53 +1100 (EST)
From: Bruce Evans <brde@optusnet.com.au>
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To: Gary Jennejohn <gary.jennejohn@freenet.de>
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Cc: FreeBSD@FreeBSD.org, FreeBSD Current <freebsd-current@FreeBSD.org>,
	Stable <freebsd-stable@FreeBSD.org>, scsi@FreeBSD.org
Subject: Re: HEADS UP: More CAM fixes.
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On Tue, 17 Feb 2009, Gary Jennejohn wrote:

> I tested this with an Adaptec 29160.  I saw no real improvement in
> performance, but also no regressions.
>
> I suspect that the old disk I had attached just didn't have enough
> performance reserves to show an improvement.
>
> My test scenario was buildworld.  Since /usr/src and /usr/obj were both
> on the one disk it got a pretty good workout.
                                   ^^^^ low
>
> AMD64 X2 (2.5 GHz) with 4GB of RAM.

Buildworld hardly uses the disk at all.  It reads and writes a few hundred
MB.  Ideally the i/o should go at disk speeds of 50-200MB/S and thus take
between 20 and 5 seconds.  In practice, it will take a few more seconds.
physically but perhaps even less virtually due to parallelism.

Bruce