errors from external USB disk

[Andrei Brezan]

On 27/02/2014 18:52, Matthias Apitz wrote:
> El día Thursday, February 27, 2014 a las 03:07:15PM +0100, Polytropon escribió:
>
>>> While copying big files from the failing disk to another with 'cp -Rp'
>>> I saw:
>>>
>>> Feb 23 18:48:07 La-Habana kernel: (da0:umass-sim0:0:0:0): READ(10). CDB:
>>> 28 00 01 cf d9 cf 00 00 0e 00
>>> Feb 23 18:48:07 La-Habana kernel: (da0:umass-sim0:0:0:0): CAM status:
>>> CCB request completed with an error
>>> Feb 23 18:48:07 La-Habana kernel: (da0:umass-sim0:0:0:0): Retrying command
>> So it's definitely a reading error here.
> I was today reading the entire disk with
>
> # dd if=/dev/da0 of=/dev/null bs=1m
>
> and after around 700 GByte it terminated with:
>
> dd: /dev/da0: Input/output error
> 712870+0 records in
> 712870+0 records out
>
> in /var/log/messages I have:
>
> Feb 27 18:01:48 La-Habana kernel: (da0:umass-sim0:0:0:0): READ(10). CDB:
> 28 00 57 05 33 80 00 00 80 00
> Feb 27 18:01:48 La-Habana kernel: (da0:umass-sim0:0:0:0): CAM status:
> SCSI Status Error
> Feb 27 18:01:48 La-Habana kernel: (da0:umass-sim0:0:0:0): SCSI status:
> Check Condition
> Feb 27 18:01:48 La-Habana kernel: (da0:umass-sim0:0:0:0): SCSI sense:
> MEDIUM ERROR asc:11,0 (Unrecovered read error)
> Feb 27 18:01:48 La-Habana kernel: (da0:umass-sim0:0:0:0): Error 5,
> Unretryable error
>
> Is there a way, to map away such bad block? Until today I was thinking
> that the firmware does this by its own, transparently.
It does but it has a limited number of unallocated sectors. If you would 
manage to attach the disk to a SATA or E-SATA controller you can use 
smartctl -a on the device and see something like this:

   5 Reallocated_Sector_Ct   0x0033   200   200   140    Pre-fail  Always       -       0

plus a few other hinting attributes. Without that we can only assume 
that it ran out of spare sectors and now it can not remap the bad ones 
anymore.

If you want to recover something from the disk with dd you can try and 
use sysutils/ddrescue so you get a best copy of what it can be read from 
the disk.

>>> I dis this already, but it does not show much:
>>> [...]
>>> Error Counter logging not supported
>>>
>>> Device does not support Self Test logging
>> Sorry, I forgot to mention: SMART usually does not work over USB.
>> Do you have the chance to attach the disk, probably a SATA drive,
>> to a "native" SATA port and try again?
> I have only laptops with USB external.
Again, maybe you have one with E-SATA around.

>
> Thanks
>
> 	matthias
>

Hope it helps,

Andrei