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When I plug in a removable 1TB USB disk in my laptop, the operations led keeps blinking for a while and then you can hear the servo mechanism resetting with a short "tack".

I'd like to recover the data.

I believe there might be some way to get the data through low level IOs.

What I believe is that the mounting process assumes the disk is OK and I should prevent this before using ddrescue or something similar.

Does anybody have a solution to this problem ?

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The information on the following page was very helpful when I had a failing disk recently:

In short, you will need enough space to store an image of the entire file system and then make a copy with ddrescue. This program will continue reading from the disk in the presence of errors, and retry failed reads.

Once you've got an image of the file system, you can then use other tools to recover your files without them failing due to read errors.

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Note that this will slow down for every sector that triggers a servo reset, and may actually require that the disk be rebooted and the process continued. Also, the logfile option of ddrescue should be specified. – hexafraction Aug 6 '12 at 18:34

If (as it seems), you're dealing with a mechanic hardware problem (not with lost or corrupted data in your HDD), it is going to be difficult to recover your data.

I'd suggest you plugged your drive to a SATA port, instead of using the USB interface (i.e., extract the HDD from its enclosure and plug it to an internal SATA port, probably in another computer, as you are talking about a laptop... find a desktop pc to do this).

If you can't manage to backup your data because the drive keeps failing, you could also try this solution, which initially sounds weird but somehow makes sense. With your -literally- frozen HDD you can try to directly copy your data or, if that fails, move up to ddrescue.

P.S. With the HDD attached to your SATA port you will be able to see its SMART status (with Disk Utility).

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