This morning when turning on a Mac laptop, it suddenly announced that an external backup disk (which was connected overnight) "can't be repaired". Disk Utility also says:

Disk Utility can’t repair this disk. Back up as many of your files as possible, reformat the disk, and restore your backed-up files.

The volume can't be mounted at all.

How can I diagnose if this failure is due to hardware problem or if it's entirely a software problem? Is it for example possible to have Disk Utility look for bad sectors? The same disk has another (exFAT) partition which seems fine.

I need to know if the whole disk is bad, and needs to be replaced, or if it's safe to use after reformatting.

The disk has never been subjected to mechanical stress (it wasn't even carried much), so I suspect it might not be a hardware failure.

  • Can you backup any files from it ? – Ruskes Jan 29 '14 at 15:37
  • @Buscar웃 As I said, the OS refuses to mount the volume, so I can't read anything off. – Szabolcs Jan 29 '14 at 17:22
  • Just asking before suggesting to reformat it. – Ruskes Jan 29 '14 at 19:36
  • @Buscar웃 I already reformatted. Fortunately it was a backup volume, so I didn't lose anything else than old versions of some files. It appears to work now, but I am not 100% comfortable. I am looking for a way to test whether this was the result of a hardware failure (and thus likely to happen again) or a software problem (i.e. no less likely to happen even if I replace the disk). – Szabolcs Jan 29 '14 at 19:52
  • This might be as good of time as any to do the stress test on it. – Ruskes Jan 29 '14 at 20:21

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