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Date:      Thu, 20 Jun 2002 04:00:39 -0700
From:      Darren Pilgrim <dmp@pantherdragon.org>
To:        freebsd-questions@freebsd.org
Subject:   Can I make FreeBSD ignore a "hard error reading fsbn"?
Message-ID:  <3D11B5D7.DDDF3FFF@pantherdragon.org>

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I'm repeatedly getting "hard error reading fsbn" messages when trying
to read out a filesystem image for mounting via vnode.

Here are the syslogged error messages:

Jun 19 14:37:43 spark /kernel: ad6: hard error reading fsbn 77267024 of 38633512-38633519 (ad6 bn 77267024; cn 76653 tn 12 sn 44)
Jun 19 14:37:46 spark /kernel: ad6: hard error reading fsbn 77267024 of 38633512-38633519 (ad6 bn 77267024; cn 76653 tn 12 sn 44) status=59 error=40
Jun 19 16:09:38 spark /kernel: ad2: hard error reading fsbn 77266944 of 38633472-38633727 (ad2 bn 77266944; cn 76653 tn 11 sn 27)
Jun 19 16:09:42 spark /kernel: ad2: hard error reading fsbn 77266976 of 38633472-38633727 (ad2 bn 77266976; cn 76653 tn 11 sn 59) status=59 error=40
Jun 20 00:58:39 spark /kernel: ad3: hard error reading fsbn 77267024 of 38633512-38633519 (ad3 bn 77267024; cn 76653 tn 12 sn 44) status=59 error=40

Notice that they all occur more or less at the same spot in cylinder
76653, and 3 of the 5 errors occur in exactly the same spot.  Is this
the result of an unmarked bad spot on the disk?  The disk came out of
a 603e PowerMac with a failing PS and overheating issues.  I can
reliably reproduce the error by simply doing a read operation across
that part of the disk with dd or an HFS volume extracting utility.  The
owner of the disk tells me that she was having constant problems with
Netscape losing its configuration data.

I've already tried changing cables.  I've already tried changing
controllers.  The power supply is adequate and stable.  The different
device nodes are due to my experimenting with different arrangements
of disks, cables, and controllers.  The disk is a Fujitsu 20GB ATA-66,
probed as "FUJITSU MPG3204AT E".  Model number on the physical label I
don't have.  DMA modes for it are disabled in the BIOS and in
hw.atamodes.  Setting it to PIO only prevents me from also getting a
DMA error when I get the hard error.

I'm trying to get the HFS+ volume image off the disk as I am testing
HFS+ support under FreeBSD with it.  Is there any way I can get around
the bad spot, to get FreeBSD to just ignore it and keep reading?  I
know the filesystem is still usable as I can read the disk in a Mac
without problems (except the Netscape thing).

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