[YLUG] Data recovery End of the story ?

[Roger Leigh]

On Tue, Jul 28, 2009 at 03:22:42PM +0100, Patrick Dupre wrote:
> On Tue, 28 Jul 2009, Roger Leigh wrote:
>
>> On Tue, Jul 28, 2009 at 12:20:23PM +0100, Patrick Dupre wrote:
>>
>>> 1) dd if=/dev/sdx of=/dev/sdy   did not work (incomplet data copy)
>>
>> Was this because the destination was too small, or an error
>> prevented a full copy?
> No, sdx was 80Go, sdy was 160 !B
>>
>>> 2) I was rescued by ddrescue /dev/sdb11 /dev/sdcx
>>
>> If dd failed while ddrescue worked, this implies that disk errors
>> caused the copy to abort.  ddrescue continues on error so that
>> it copies every /readable/ block, but if particular blocks are bad
>> they won't get copied.  The implication of this is that your disk
>> isn't just corrupted, it's broken and needs replacing.
>
> I do not think so, the partition table was just a bit messy.
> and the recover was perfect after a fsck -y
> the partition was in lost+found dir with a # number.
> The rest seems perfectly OK.

dd copies raw blocks from your disk.  Whether the partition table was
messy or not is most likely irrelevant.  The only circumstance where
it could fail is if the partition extends over the upper size limit
of the disc (in which case you'll still have as full a backup as is
practical).  If this was not the case, then your disc is not well;
fsck might not have detected silent corruption of your data (as
opposed to the filesystem metadata).  If anything ended up in
lost+found, then /something/ was wrong.


Regards,
Roger

-- 
  .''`.  Roger Leigh
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