[linux-lvm] Effects of XXremove and then XXcreate on fs

[linux-lvm] Effects of XXremove and then XXcreate on fs

[Joshua Aune]

If an LV is [lv,vg,pv]removed and then re[pv,vg,lv]created not using the
backup file, what are the effects on the old LV?
 is it possible to remove the new created LV/VG/PV and recreate using
  the backup file and still access the volume?
 or is there some on-disk metadata from the original LV that got hosed
  by the creation of the new LV?

I am trying to recover a system that had the above done to it along with
possibly having some other problems, and am trying to weed out possible
causes of failure.  I do have the backup/ file now and will be
attempting this as soon as I can restore the block devices from backups
(another 6 hours).

As far as I can tell the LV/VG/PVs were not resized or changed at all
from the time it was created to the time the underlying hardware
crashed...

Are there any gotcha's trying to do this?

Thanks,
Josh

Re: [linux-lvm] Effects of XXremove and then XXcreate on fs

[Luca Berra]

On Fri, Jun 16, 2006 at 09:18:07AM -0600, Joshua Aune wrote:
>If an LV is [lv,vg,pv]removed and then re[pv,vg,lv]created not using the
>backup file, what are the effects on the old LV?
> is it possible to remove the new created LV/VG/PV and recreate using
>  the backup file and still access the volume?
> or is there some on-disk metadata from the original LV that got hosed
>  by the creation of the new LV?
>
>I am trying to recover a system that had the above done to it along with
>possibly having some other problems, and am trying to weed out possible
>causes of failure.  I do have the backup/ file now and will be
>attempting this as soon as I can restore the block devices from backups
>(another 6 hours).

from the lvrcreate manpage:

       -Z, --zero y/n
              Controls zeroing of the first KB of data in the new logical vol-
              ume.
              Default is yes.

              Warning: trying to mount an unzeroed logical  volume  can  cause
              the system to hang.

you might be able to recover the filesystem using an alternate superblock if you wiped
the first KB of fs data.

L.

-- 
Luca Berra -- bluca@comedia.it
        Communication Media & Services S.r.l.
 /"\
 \ /     ASCII RIBBON CAMPAIGN
  X        AGAINST HTML MAIL
 / \