[kwlug-disc] Media errors on a USB disk

[Eric Gerlach]

On Wed, Oct 20, 2010 at 10:08 AM, Khalid Baheyeldin <kb at 2bits.com> wrote:
> For the weekly backup, I am now getting this error:
>
> [2388063.441067] sd 13:0:0:0: [sdb] Result: hostbyte=DID_OK
> driverbyte=DRIVER_SENSE,SUGGEST_OK
> [2388063.441073] sd 13:0:0:0: [sdb] Sense Key : Medium Error [current]
> [2388063.441077] sd 13:0:0:0: [sdb] Add. Sense: Unrecovered read error
> [2388063.441080] end_request: I/O error, dev sdb, sector 177045897
> [2388064.495756] sd 13:0:0:0: [sdb] Result: hostbyte=DID_OK
> driverbyte=DRIVER_SENSE,SUGGEST_OK
> [2388064.495762] sd 13:0:0:0: [sdb] Sense Key : Medium Error [current]
> [2388064.495765] sd 13:0:0:0: [sdb] Add. Sense: Unrecovered read error
> [2388064.495768] end_request: I/O error, dev sdb, sector 177045897
>
> If I replace the disk with an identical brand (but has a different make
> of disk inside), I get other errors.
>
> These two disks have been stable and trouble free for about 2 years,
> with no issues.
>
> My questions are:
>
> 1. Short of dd if=/dev/sdb, is there a way to detect blocks?

SpinRite.  Proprietary, but the best I know of.

> 2. Do we have a way to add the bad blocks to a list that the operating
> system
> should ignore, like we had in the old days?

No, now drives do this internally.  Drives keep a percentage of their
sectors as spares, and swap them in when needed.  SpinRite helps the
drive find those bad blocks, recover the data, and then relocate the
blocks.

> 3. Could this be a quirk of some sort? How do I know for sure if it is
> really a media problem or some bug/quirk?

No idea.  I don't even know what those errors mean, so I can't even
confirm for sure that it's bad blocks.

Cheers,

Eric