sumofungus

mainly linux, some windows…

making backup copies of damaged dvds using ddrescue

with 5 comments

I would normally use AnyDVD (on Windows) to take a backup of a DVD with copy protection, but is doesn’t seem to handle read errors very well (e.g. discs have small scratches) and copies fail.

GNU ddrescue (gddrescue, ddrescue, NOT dd_rescue) on linux is supposed to be better at handling small errors and is designed to handle read errors.

Using ddrescue

So far I have found that the best way is to take an quick(ish) initial copy;

ddrescue -b 2048 -n -v /dev/sr0 image.iso image.log

This reads the whole disk once, marking any bad blocks as “non-trimmed”. It then reads again in the other direction retrying any bad blocks. Any blocks that still fail are “trimmed” then marked as non-split. There is no further processing after this because of the -n option.

If there are any read errors do another pass using the direct option (-d). You must also specify the number of retries that bad sectors get (-r), otherwise they will be ignored;

ddrescue -b 2048 -d -r 3 -v /dev/sr0 image.iso image.log

… if there are further errors then you can use the -R (retrim) option to retry full sectors (taken from Forensics Wiki). This will try the any bad sectors in a different order which might help read some (according to the ddrescue documentation, see link below);

ddrescue -b 2048 -d -r 3 -R -v /dev/sr0 image.iso image.log

I have yet to investigate using different drives to read the disc for another pass, but this might also help.

Other Notes

I don’t think this method (using ddrescue)  removes any copy protection.

Links

Full manual for GNU ddrescue; http://www.gnu.org/software/ddrescue/manual/ddrescue_manual.html

Reading discs might take a long time; http://old.nabble.com/10-days-for-7.8gig–td21461792.html

Good documentation about Data Recovery and ddrescue; https://help.ubuntu.com/community/DataRecovery#Data%20Recovery%20from%20damaged%20filesystem%20or%20drive

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Written by sumofungus

January 19, 2010 at 2:07 AM

Posted in Uncategorized

5 Responses

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  1. […] or 1/8. Triggered by Cactus wireless flash trigger V4. ddrescuing an old CD Image by Kai Hendry sumofungus.wordpress.com/2010/01/19/making-backup-copies-… I strongly suggest migrating all data onto a couple of 1TB hard drives and binning the compact disc […]

  2. im currently trying to recover a scratched dvd, using a second drive, after the first one was able to recover almost everything but a small amount of blocks. i’m getting positive results and encourage everyone to try this approach if there’s a second (or more) drive at hand…

    thanks for the tutorial, it has been very helpful. maybe you want to add some tips for physically improving a scratched disc, like carefully using toothpaste with fine abrasives to soften the scratches?

    xmoex

    February 21, 2012 at 5:56 PM

  3. Good little how to, easy to follow & strait to the point. One thing I find helps recover a few extra errors when it gets stuck on ‘time since last succesfull read’ is to eject the disk & turn it a little and do step 3 again.

    Mark

    January 15, 2013 at 12:11 PM

  4. It is still very helpful!!

    Andreas

    August 28, 2016 at 9:19 AM


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