ext3 corrupted

[Allen Taylor]

On Mon, Jul 23, 2007 at 09:34:33AM -0400, Madison Kelly wrote:
> Lennart Sorensen wrote:
> >On Sat, Jul 21, 2007 at 05:37:19PM -0400, Marc Lijour wrote:
> >>I have a drive that got corrupted (just before it started to send SMART 
> >>alerts). I can't mount it and I get this error message:
> >>
> >>EXT3-fs error (device sda12): ext3_check_descriptors: Block bitmap for 
> >>group 896 not in group (block 16777317)!
> >>
> >>I can't mount it as ext2 either, and I can't mount sda either. auto as 
> >>type does not work either.
> >>
> >>Running fsck and accepting all actions with a 'y' seems to have no 
> >>effect. I can't mount the disk and when I get to do fsck again I get the 
> >>same actions.
> >>
> >>dd works.
> >>
> >>Do you know a way to get the data back?
> >>
> >>Thanks a lot (!)
> >
> >Well you could try fsck with the -b 8193 option to tell it to use an
> >alternate superblock.  Might work.
> >
> >If the drive is actually going bad, certainly the advice of letting it
> >cool off is a good one.  I actually managed to recover all the data from
> >a failed drive for my sister that refused to even try to boot, by trying
> >it out right after getting home in the middle of winter while the
> >computer was probably at about -10C.  Read everything perfectly and got
> >all the data of it and onto new dists (I replaced it with raid1).
> >Didn't even get a single read error, it just ran perfectly.  I have read
> >that a lot of recovery people will actually freeze the drive before
> >trying to read it since it apparently works quite well in many cases
> >without having to do anything complicated.
> 
> Just be careful to do the post-freeze DR in a low humidity environment! 
> Condensation could make things worse, if you are not careful. :)

To address the humidity issue, I place the drive in a "zip lock" bag
before putting it in the freezer. The next day I only open the zip lock
bag enough to attach power and data cable and run that way.

I've done this a few times with good results about half the time. The
other half I suspect would be only be recoverable by the above mentioned
experts.  YMMV

Allen

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