[ 323.268251] sd 6:0:0:0: [sdc] Result: hostbyte=DID_ERROR driverbyte=DRIVER_SENSE
[ 323.268257] sd 6:0:0:0: [sdc] Sense Key : Hardware Error [current]
This is a hardware error. So either your disk or your USB-Sata controller is defective. What did the NAS status led do? When that was 'alternating white/red' or 'solid red', then I'm afraid your disk is dead. When it was something else, then the USB-Sata controller could be the problem, or the power supply (or your USB port? Don't think so).
On the other hand, the partition table is recognized, so *something* is still alive. You could try to clone your data partition to another disk using ddrescue
. (That will last a *long* time, maybe several days). Then you could try xfs repair (and/or PhotoRec
, depending on the nature of the data) on the copy (or the copy of the copy, if you have the diskspace).
When your data is really valuable, you should stop now, and bring the disk to a professional data recovery company.