TestDisk image vs ddrescue for recovering data from a defective hard drive

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QUESTION :

I am trying to duplicate a “defective” hard drive (making strange noises after it fell on the floor).

After some research, I discovered TestDisk and the “Image Creation” tool to clone the disk. I successfully managed to make an image from the drive.

Nevertheless, it annoys me they don’t mention their own solution in the “Damaged Hard Disk” section of their website they advise to use ddrescue.

I understand that I need to use tools especially created for damaged drive, in order to protect it.

What are the differences between the two tools (TestDisk image creation tool and ddrescue)? ddrescue more appropriate in my case?

ANSWER :

This can all seem confusing, but the best way to understand it is this: One tool is designed to deal with logical level issues and the other is designed to deal with block level issues.

  • Logical Level: TestDisk is designed to deal with logical-level partition issues
  • Block Level: DDRescue is designed to go deeper on the disk, past the partition layer, to recover data on a raw block level.

Here is how each tool describes itself from it’s own homepage:

  • TestDisk: “TestDisk is powerful free data recovery software! It was primarily designed to help recover lost partitions and/or make non-booting disks bootable again when these symptoms are caused by faulty software: certain types of viruses or human error (such as accidentally deleting a Partition Table). Partition table recovery using TestDisk is really easy.”

  • DDRescue: “GNU ddrescue is a data recovery tool. It copies data from one file or block device (hard disc, cdrom, etc) to another, trying hard to rescue data in case of read errors.”

Which tool is “best” or most appropriate in your case where your drive has fallen on the floor and now makes odd noise? My guess would be DDRescue would be your best bet. Your are not dealing with a logical disk issue but rather a physical failure and DDRescue is designed to work around physical issues that might make other data recovery packages choke and die.

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