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Date:      Tue, 26 May 1998 15:06:33 -0700
From:      Mike Smith <mike@smith.net.au>
To:        Nate Williams <nate@mt.sri.com>
Cc:        Mike Smith <mike@smith.net.au>, Michael Robinson <robinson@public.bta.net.cn>, freebsd-stable@FreeBSD.ORG
Subject:   Re: Bug in wd driver 
Message-ID:  <199805262206.PAA01738@dingo.cdrom.com>
In-Reply-To: Your message of "Tue, 26 May 1998 16:58:27 MDT." <199805262258.QAA09021@mt.sri.com> 

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> > > Having a bad spot on a disk shouldn't make the disk *totally* unusable,
> > > as every other 'significant' OS can deal with fine.
> > 
> > This isn't a "bad spot" in the traditional sense - this is the disk
> > firmware failing.
> 
> No, this is a bad spot on the disk.

I'm sorry Nate, but if it was a bad spot the error register would be 
nonzero.  Please check the originally quoted diagnostic for the actual 
status/error register values.  Also note that DRQ would not be set if 
the timeout had occurred too soon.

The drive has failed to deliver an interrupt upon completion.  As far 
as I am able to determine (given no access to the system or other data) 
this is a disk firmware fault.  The most reasonable justification for 
this is catastrophic failure due to corrupted firmware-level metadata.

> > A "bad spot" gives you a recognisable, and recoverable, error.
> 
> Only if the bad spot can be remapped 'magically' behind the scenes, or
> the spot is 'recoverable.  When your bad-sector table is filled, the
> hard-disk is saying 'I can't read this anymore, so quit trying'.  The
> FreeBSD driver says 'Please, try again', and again, and again, and
> again...

Actually, it eventually gives up.  (Check the source if you don't 
believe me.)

But that's not the error we're seeing here, as you would know if you 
were familiar with the original report and the interface in question.

> > Note that DOS-derived operating systems will often dump their cookies in
> > a similar fashion under the same circumstances (exact results seem to 
> > vary, and I don't have a drive I can test this with anymore, having 
> > consigned my last one to the dump before moving).
> 
> Not in my case.  Win95/DOS was able to recognize this and map it out.

We're not talking about your case, in this case.

> > > This is also why I was w/out a laptop for 5 months, since our driver
> > > couldn't get past the bad sector on the boot partition when it went bad
> > > and everytime fsck tried to read it it locked up the computer. :(
> > 
> > So don't fsck it; I talked you through solving that problem, and you 
> > ignored me.  8)
> 
> I couldn't *NOT* fsck it since init was were the bad-blocks was
> located. (I think it was the inode).  All attempts to fix it or
> workaround it didn't work, so I punted on it.

That's the same response : "fixing it is too hard".  I suggested 
another machine, as well as sources for the connectors involved.

> By the time I got DOS to remap it, I gave up on using FreeBSD on it,
> since I figured it was only a matter of time before another bad-spot
> showed up and I'd be in the same boat.

Just wait 'till one shows up in one of DOS' critial areas.  It's all 
relative.

-- 
\\  Sometimes you're ahead,       \\  Mike Smith
\\  sometimes you're behind.      \\  mike@smith.net.au
\\  The race is long, and in the  \\  msmith@freebsd.org
\\  end it's only with yourself.  \\  msmith@cdrom.com



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