[ILUG] HOWTO recover a borked 3ware RAID-1 array (long)

[Pádraig Brady]

Ronan Cunniffe wrote:
> Hi all,
>    3ware 7000 & 8000 series RAID controllers have a nasty habit of
> corrupting their proprietary bits and saying "disk incomplete" if
> they're shut down at the wrong moment.  I've just finished sorting one
> out (*cough* _permanently_), and maybe this howdunnit might be useful.

cool, thanks.

> Step 1) Find the real disk layout.
>    The 3ware sticks its proprietary bit at the start of the disk.  Where
> does the "real" data start?  In my case, the proprietary stuff took up
> 1024 sectors.  I know this because:
> 
>       for i in `seq 1 2048`; do dd if=/dev/hda of=diskblock.$i bs=512
> skip=$i count=1; done
>       file diskblock.* | grep boot

minor optimisation to not have temp files and break out early:

for i in `seq 0 2048`; do
    sudo dd if=/dev/sda bs=512 skip=$i count=1 2>/dev/null |
    file - |
    grep -q boot &&
    echo sector $i &&
    break
done

> 
> gave me:
> 
>       diskblock.1024: x86 boot sector
> 
> Step 2) Find the partition table
>    I tried:
>         losetup /dev/loop0 /dev/hda -o 524288
>         fdisk -l /dev/loop0
> 
>    and was rewarded with the truly weird, but accurate:
> 
>    Disk /dev/loop0: 80.0 GB, 80007761920 bytes
>    255 heads, 63 sectors/track, 9728 cylinders
>    Units = cylinders of 16065 * 512 = 8225280 bytes
> 
>   Device Boot      Start         End      Blocks   Id  System
>    /dev/loop0p1              1          129     1031610  82  Linux swap
>    /dev/loop0p2   *        130        429    77......   83  Linux
> 
> 
> Step 3) Mounting the partition - the off-by-one error
>    Note that tracks are numbered from 1, not 0, so the start of track
> 130 is at 16065*512*129.
> 
>    so:
>        losetup /dev/loop0 /dev/hda -o $((524288+(129*512*16065)))

Would my lomount.sh script help?
http://www.pixelbeat.org/scripts/lomount.sh

./lomount.sh /dev/loop0 2 /mnt/data

>    If you want to double check with dd(1) and file(1) as before, looking
> for confirmation you have an ext2 fs starting here, 'dd bs=512 count=1'
> won't work, because the signature of an ext2 fs is (according to
> /usr/share/file/magic (on Debian)) 1080 bytes in....
> Step 4: subject the 3ware to some torsion testing and use the onboard
> IDE and the md driver instead.

:)

Pádraig.