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Date: Tue, 31 Oct 2000 00:52:11 +1100
From: Andrew Morton <andrewm@uow.edu.au>
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To: Pierre Etchemaite <petchema@concept-micro.com>
CC: "Mohammad A. Haque" <mhaque@haque.net>,
        linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: ide/disk perf?
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Pierre Etchemaite wrote:
> 
> Le 30-Oct-2000, Mohammad A. Haque ?crivait :
> > Could someone who knows ide and drive inside and out (Andre?) please
> > take a look at these figures? Am I forgetting to do something (or doing
> > something I'm not suposed to) to get the best numbers? I thought I'd be
> > able to get more than ~4MB/sec off the HPT366 and a UDMA66 drive.
> 
> It could be unrelated, but I had problems several times with Maxtor drives
> recently; Their performances are usually high (some models give >20 Mb/s
> both reads and writes), but under some conditions that I couldn't narrow down
> yet, the read throughput is stuck to the floor (a few megabytes/sec) until
> next reboot. The write performance is always ok.

I had the same problem with Seagate ST313021A (13 gig) drives on
BP6/HPT366/UDMA66.  Initial throughput reported by `hdparm -t' was 22
megs/sec which would slowly wilt to 5 megs/sec.

I discovered that sending _any_ reconfiguration command to the drive -
even one which was not supported by that particular drive - would bring
the performance back.

So when it goes slow, try running, say, `hdparm -A1' and see what
happens.

Andre and I scratched each others heads for a while, suspected a
firmware bug.  He sent an email to a contact at Seagate.  This was in
April, so I guess that person is a very slow typist.
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