-=> Arelor wrote to Dumas Walker <=-
Ar> @MSGID: <6022532A.385.dove-unix@palantirbbs.ddns.net>
Ar> @REPLY: <6021A2F5.2616.dove-nix@capitolcityonline.net>
Ar> Re: ddrescue
Ar> By: Dumas Walker to ALL on
Ar> Mon Feb 08 2021 03:45 pm
> I have been trying to use ddrescue to make a good copy of a DVD that only
> works in some of my DVD players. I actually got it to work with one DVD,
> but the other one gets so far and then, after several hours, the screen
> looks like this:
>
> ***
> # ddrescue -v -b 2048 -r 4 /dev/sr0 D1.iso D1.log
> GNU ddrescue 1.23
> About to copy 7255 MBytes from '/dev/sr0' to 'D1.iso'
> Starting positions: infile = 0 B, outfile = 0 B
> Copy block size: 32 sectors Initial skip size: 64 sectors
> Sector size: 2048 Bytes
>
> Press Ctrl-C to interrupt
> ipos: 4415 MB, non-trimmed: 360116 kB, current rate: 0 B/s
> opos: 4415 MB, non-scraped: 0 B, average rate: 79775 B/s
no
Ar> n-tried: 1716 MB, bad-sector: 0 B,
> error rate: 8192 B/s
> rescued: 5179 MB, bad areas: 0, run time: 18h 2m
> pct rescued: 71.37%, read errors: 5569, remaining time: n/a
> time since last successful read: 16h 30m 43s
Co
Ar> pying non-tried blocks... Pass 5 (forwards)
> ***
>
> Note that the last successful read time is over 16 hours. At this point,
> the numbers in the left column have long since quit incrementing, while the
n
Ar> umbers (that are not 0) in the other two colums
> are the only ones going up.
>
> I have searched on the internet about this. Some folks talk about theirs
> going days without ever stopping on its own. Others point out that
> sometimes you can CTRL-C out and the iso you get will be mostly OK. Mine
unf
Ar> ortunately was not. :)
>
> Is there anything I should think about changing on the command line to get
be
Ar> tter results?
>
>
> * SLMR 2.1a * I am Popeye of Borg. Prepare to be askimilgrated.
>
Ar> I don't do a lot of optical media rescuing with ddrescue, but the idea
Ar> is that you have to perform the reads using multiple devices.
Ar> Say you have a bunch of defective sectors. Some optical media reader is
Ar> capable of reading 33% of them. Another media reader can read 50% of
Ar> them. And another media reader can read 39% of them. Hopefully if you
Ar> run ddrescue with each reader, and put the results together, you can
Ar> rebuild the whole iso or at least the most of it.
Ar> You could run a round of reads using the -n switch, which should speed
Ar> things up quite a bit. Reduce the number of retries too - there is no
Ar> point in trying 4 times for the sector in a first run. You will
Ar> retrieve less data with each pass, but the thing is that if 30% of the
Ar> image is unreadable after the first run you know you can put the DVD
Ar> into the trash and need waste no more time :-)
Trying a different drive will probably help more than using different command
line switches. IF the problem is degradation of the media, subtle differences
in the lasers between drives can lead to different results. You mention it
worked on one drive, so do you have someone elses machine you can use? IS the
disk scratched?
I have found that some drives might barf on one disk where another doesn't.
I'd be interested to know how you stick multiple failed ISO's together. I
found my Doom 3 CD's (original, not pirate, two of them would fail one my
desktop, but I was able to read them on my laptop.
IF the degradation is affecting a portion of the disk (ie, its not just one or
a few sectors), well, unless you can get it working on another drive, its
likely gone.
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