Re: Any chance to recovery btrfs raid-0 after accidental format of one volume?

Re: Any chance to recovery btrfs raid-0 after accidental format of one volume?

[Dante]

Bad case of user error here but I managed to reformat one half of a
btrfs volume that was set up with metadata raid-1 and data raid-0.

I can mount the remaining half degraded, and can see all of the files,
but half their content is missing.

I=92m just wondering whether, since all the metadata is intact, and
since (most of) the data on the partition that I reformatted has not
actually been over-written, whether it is conceivable that I can
recover most of my files by somehow reincorporating the second volume
into the array?

The important stuff is all backed up (I hope) so this is more of
academic interest...
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Re: Any chance to recovery btrfs raid-0 after accidental format of one volume?

[Tomasz Chmielewski]

> Bad case of user error here but I managed to reformat one half of a
> btrfs volume that was set up with metadata raid-1 and data raid-0.

It won't help you - but did you format it with mkfs.btrfs, while it was mounted?

mkfs.btrfs behaves very dangerously here.


For example, we have a block device in use:

# cat /proc/swaps 
Filename				Type		Size	Used	Priority
/dev/md0                                partition	10233276	0	-1


mkfs for other filesystems will refuse to touch it, because it's in use:

# mkfs.ext4 /dev/md0
mke2fs 1.41.14 (22-Dec-2010)
/dev/md0 is mounted; will not make a filesystem here!

# mkfs.xfs /dev/md0
mkfs.xfs: cannot open /dev/md0: Device or resource busy




mkfs.btrfs doesn't see a problem in creating a filesystem on a mounted block device:

# mkfs.btrfs /dev/md0

WARNING! - Btrfs Btrfs v0.19 IS EXPERIMENTAL
WARNING! - see http://btrfs.wiki.kernel.org before using

fs created label (null) on /dev/md0
	nodesize 4096 leafsize 4096 sectorsize 4096 size 9.76GB
Btrfs Btrfs v0.19



-- 
Tomasz Chmielewski
http://wpkg.org

RE: Any chance to recovery btrfs raid-0 after accidental format of one volume?

[Dante]

> > Bad case of user error here but I managed to reformat one half of a
> > btrfs volume that was set up with metadata raid-1 and data raid-0.

> It won't help you - but did you format it with mkfs.btrfs, while it was mounted?

No I formatted as ext4 while off-line.

Thanks for the feedback.

I guess I just kiss the files goodbye and move on.

Re: Any chance to recovery btrfs raid-0 after accidental format of one volume?

[Hugo Mills]

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On Wed, Sep 07, 2011 at 09:00:21AM +1000, Dante wrote:
> > > Bad case of user error here but I managed to reformat one half of a
> > > btrfs volume that was set up with metadata raid-1 and data raid-0.
> 
> > It won't help you - but did you format it with mkfs.btrfs, while it was mounted?
> 
> No I formatted as ext4 while off-line.
> 
> Thanks for the feedback.
> 
> I guess I just kiss the files goodbye and move on.

   In this instance, it's almost certainly going to be faster to
recover from your backups than it is to attempt to reconstruct the few
files that you can from the bits that aren't missing.

   Hugo.

-- 
=== Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk ===
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    --- Don't worry, he's not drunk. He's like that all the time. ---    

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