Rescue from failing drives #24146691

Thanks for your rapid response. I searched dd_rescue and most articles are too technical for me. Sounds like it's an executable program. Can you tell me more explicitly what you have in mind? I'm not at all clear whether you propose I can do this in situ to a new drive in a spare bay in the NAS, or in a drive enclosure, etc. Also, another thread I just found (http://www.readynas.com/forum/viewtopic.php?f=65&t=75358) suggests I should back up to USB first anyway. Which would you do first - USB back up or dd_rescue? I won't respond again tonight - it's 23:10 UK time. Thanks again in advance.