Archived from groups: comp.sys.ibm.pc.hardware.storage (
More info?)
"Mike Tomlinson" <mike@NOSPAM.jasper.org.uk> wrote in message news:bXwFRnBTJh+BFw9e@jasper.org.uk
> In article <ctbkt92uof@enews4.newsguy.com>, Eric Gisin <ericgisin@hotmail.com> writes
>
> > Since the TOC is unreadable, how can Linux find the session? I assume
> > /dev/cdrom is the first or last session.
>
> /dev/cdrom is a block device, which means reading from it is equivalent
> to reading from the first LBA on the disk onwards.
>
> Thanks to all for the help and suggestions. There's a lot of tools out
> there; it's just finding out what they are, and I appreciate the
> pointers.
>
> Bart's SCSItool was able to determine that the session on the disk has
> 206,000 blocks written (about 402Mb), but was unable to read any
> actual data using the sector hexdump.
>
> ISObuster was able to determine that the disc has one session and one
> track of 402Mb (correct) but was taking a very long time. I'll come
> back to ISObuster if readcd (see below) doesn't work.
I have found that successfully reading bad sectors is speed dependent
(one sector may read best at 4-speed while an other reads best at 8-
speed) and that there are 2 (or 3) speeds that work best. Also, chan-
ging speeds during retries sometimes gets a badly readable sector.
You can change speed using Joerg Fiebelkorn's CD Throttle.
Also, a hot drive reads worse and the more retries are needed and the
more the drive is slowing down and speeding up again during retries,
it hots up faster. I get the best results when the drive is cold.
I have also found that what one drive can't read, another might, and
vice versa. When a drive that reads the TOC succesfully but can't
read a specific file (using ISOBuster) it may be possible to read it
on another drive (even though that drive won't read that TOC), by
using Extract From-To and the file info (begin sector, end sector)
provided by the TOC on that other drive.
>
> I have downloaded and built dd_rescue but not yet tried it.
>
> Also tried polishing the disc with silicone polish to see if masking
> scratches helped. For information, the disc is a no-name one with silver
> top and blue dye. It has the serial number 25E805241232C09. It had
> a paper label attached to the top surface which I removed using label
> remover. The top is undamaged.
>
> Using Linux 'cdrecord -atip' says the disk type is "Long strategy type,
> cyanine, AZO or similar", the manufacturer index is 22, and the maker
> is Ritek.
>
> I'm now processing the disc with Linux readcd (part of Joerg Schilling's
> cdrecord suite) and an AOpen CRW-4850 drive. This is reporting
> "error on sector n corrected after x tries", and the sector number is
> incrementing slowly, so it appears to be getting somewhere. I'll leave
> it running and report back. The command used is "readcd dev=2,0,0
> f=/tmp/wos.iso -v -noerror".
>
> Thanks again to all for the suggestions.