Obligatory recommendation to use ddrescue as a first pass. Personally I've been helped in at least three ways by this: * ddrescue doesn't retry immediately; i

Obligatory recommendation to use ddrescue as a first pass. Personally I've been helped in at least three ways by this: * ddrescue doesn't retry immediately; it tries to get as many readable sectors/blocks as possible first and then goes back and retries. When there are many bad sectors this is way more efficient than retrying N times at each bad sector while additional readable data is sitting on the bad device. * ddrescue has configurable retries and its map file to perform rescue over any interruptions. If a device loses power or overheats and stops responding or for whatever other reason you don't have to get everything off the failing device in one pass. * If you have two failing RAID1 devices you can ddrescue from one and then from the other to get as much data as possible. If you need to recover audio CDs, use cdparanoia which takes a similar approach but uses a lot of speculative re-reads to avoid bad reconstruction efforts by some CD drives as much as possible.