[kwlug-disc] Media errors on a USB disk

Andrew Sullivan Cant acant at alumni.uwaterloo.ca
Wed Oct 20 13:12:20 EDT 2010


As a FLOSS alternative and if you are using ext2/ext3/ext4 then e2fsck 
will also check for bad blocks and do corrections.

e2fsck -c -y /dev/sdb
-c will try to detect and fix bad block by adding then to the bad block 
inode
and -y will answer yes to doing all of the corrections. Which is 
probably what you want most of the time.


I have not tried SpinRite so I don't know what additional magic it might do.


Andrew

On 20/10/10 10:33 AM, Eric Gerlach wrote:
> 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
>
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