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Date:      Sat, 30 Nov 2002 13:35:20 +0000
From:      David Malone <dwmalone@maths.tcd.ie>
To:        Daniel Geske <daniel.geske@yoc.de>
Cc:        'Daniel Geske' <danielgeske@gmx.net>, freebsd-scsi@FreeBSD.ORG
Subject:   Re: fsck: PLEASE RERUN FSCK - does not fix problem :-(
Message-ID:  <20021130133520.GA83659@walton.maths.tcd.ie>
In-Reply-To: <001901c29863$bb15d670$a52efea9@Bowman>
References:  <20021130105251.GA82084@walton.maths.tcd.ie> <001901c29863$bb15d670$a52efea9@Bowman>

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On Sat, Nov 30, 2002 at 12:29:20PM +0100, Daniel Geske wrote:
> Thanks for your reply. Is there anything I can do like make the disk
> skip the bad parts and keep on using the parts that are still good?

As I unserstand it, the "MEDIUM ERROR" is the disk saying that it
tried to read the requested block, but couldn't. SCSI Drives should
be clever enough to be able to map these blocks to spare blocks
elsewhere on the disk, but this remapping can only be done on a
write. (This is usually enabeled by default, but you may need
to enable it with camcontrol.)

So, if the information on the disk isn't too important you can try
rewriting the sectors on the disk to get the disk to remap them.
Something like "dd if=/dev/zero of=/dev/da1" should work, but
remember it will wipe the information on the disk.

While this often works, if the disk is going bad you find that it
will quickly reach a state where you are loosing blocks often enough
that the disk is useless and you're better off buying a new one.

(On our busier disks we probably see one or two blocks go bad a
month, as shown by "camcontrol defects daX". Disks that are going
bad any faster than that should be backed up before they die...)

	David.

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