Recover specific files from a damaged hard drive

Question

I'm trying to recover some 3-5GB of NEF files which were not yet backed up at the time of the crash.

This is a 418GB ext4 partition and when mounted with -o ro,noload I can list the directory where the files are but I get an error if I try to copy them. I'm currently running ddrescue -n --direct --no-trim --sector-size=4096 and while it started reasonably fast, it has since slowed down considerably. After a restart six hours ago, currently the average speed is about 38KB/s. So far it has rescued 7.5GB.

Given the low speed of ddrescue - is there any way to copy only the files that I need? I'm not interested much in the rest of the disk.

Answer 1

I'll answer my own question, but feel free to post another answer if you have a better idea.

Here is what I did. First, I mounted the partition as read-only:

mount -o ro,noload /dev/sdb6 /badhdd

Then I used find to run ddrescue on each file:

mkdir ~/rescue
mkdir ~/rescue-log
find /badhdd/path/to/directory -type f -name "*.NEF" -exec ddrescue -vvvv -P1 -n --no-trim /badhdd/path/to/directory/{} ~/rescue/{} ~/rescue-log/{} \;

For any files with errors I did:

ddrescue -vvvv -P1 --reverse /badhdd/path/to/directory/{} ~/rescue/{} ~/rescue-log/{}

After 72 hours I have recovered 65 files out of just over 400 with an average size of 10MB. The speed varies a lot - it takes less than 10s to recover some files, while others take 5-6 hours.

This means that if I manage to recover only the files that I actually need, the recovery will take about 18-20 days, as opposed to over 120 for the entire partition.