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Date: Wed, 12 Mar 2003 22:28:46 +0100
From: Andries Brouwer <aebr@win.tue.nl>
To: torvalds@transmeta.com (Linus Torvalds)
Cc: linux-kernel@vger.kernel.org
Subject: Re: bio too big device
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On Wed, Mar 12, 2003 at 05:59:03PM +0000, Linus Torvalds wrote:

> >We have seen *zero* drives that do not understand 256 sector commands.
> >Maybe such drives exist, but so far there is zero evidence.
> 
> That is definitely not true.  We definitely _have_ had drives that
> misconstrue the 256-sector case. It's been a long time, but they
> definitely exist.

I disagree. If you have any proof, please show it.

Let me repeat:
We have seen *zero* drives that do not understand 256 sector commands.

We have seen *one* drive (a six years old Maxtor 7850AV) that could not
sustain heavy load with max # secs set to 256, while it behaved better
with max set to 255.

But we have seen lots of old old drives that show all kinds of errors.

> The right limit for IDE is 255 sectors, and doing 256 sectors WILL fail
> on some setups.

Paul remarked: "So the 255 (or even the old 128) fixes things vs. 256,
but I'd feel better being 100% sure why. Is 255 a "fix" or a perturbation
that happens to paper over something else?"

I think there is no good reason to limit us to 255 sectors.

(And no reason for blacklists either - there is just no good evidence
that something is systematically wrong with 256 sectors for any brand or
model. Things would change if a second Maxtor 7850AV owner could confirm.)

Andries

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