[Btrfs-devel] reversing the effects of mkfs.btrfs?

[Peter Teoh]

Thank you Chris.

I did a fsck.ext3 but no help either, as the number of "y" I must
enter is so large and never ending (for a simple 50X1M files, 200M
partition), that I eventually have to use the automatic "yes" to all
question to complete the fsck.

And lots of files are found in the lost+found directory, but none
match the initial pattern I have created.

THanks for the tip, shall try further.

On Mon, Apr 28, 2008 at 8:31 PM, Chris Mason <chris.mason at oracle.com> wrote:
> On Sunday 27 April 2008, Peter Teoh wrote:
>  > Ok, I have done some experiments:
>  > :-( :-( :-( :-( :-( :-( :-( :-( :-( :-( :-( :-( :-( :-( :-( :-(
>  >
>  > This is no good.
>  >
>  > I did some test on a 100M partition.
>  >
>  > 1.   create/mount a ext3 fs.
>  > 2.   create 50 identical files (with random contents inside).
>  > 3.   dismount it.
>  > 4.   do a dd backup of the image.
>  > 5.   execute mkfs.btrfs on it.
>  > 6.   do a dd backup of the image.
>  > 7.   compare incrementally the hexadecimal output of the two dd image
>  > above.
>  >
>  > The results?   Disaster, lots of binary diff.   Starting with 0x400 offset:
>
>  mkfs.btrfs zeros the first and last 2MB of the drive.  As a percentage of the
>  40GB, this is pretty small.
>
>
>
>  >
>  > Doing a mkfs.ext3 after the mkfs.btrs does not restore back any
>  > information, if not destroying even more information.
>
>  mkfs won't restore information, it is meant to initialize things and remove
>  markers from other filesystems.  But, 99% of the data is still going to be
>  there.
>
>  A quick search found:
>
>  http://www.recoveryourdata.com/linux-data-recovery.html
>
>  People on the ext3 development lists might have other suggestions.
>
>  -chris
>



-- 
Regards,
Peter Teoh