[linux-lvm] How to recover data corrupted by vgcreate

[張廷州]

Hi,

There is no backup information available in /etc/lvm/archive to restore VG to original configuration.
Unfortunately the root directory is also in LVM partition.
So, "vgcfgrestore" did not solve the problem.
I also tried to create new LV by "lvcreate" to match with the existing LV.
The problem is I have no idea about the size of old LV.
I just gave a random size in "lvcreate" command.
But, I could not mount the file system because of bad superblock.
I don't know what I missed. Maybe the size is critical to do the matching.
Is there any reverse procedure I can do to recover VG by the existing LV information?
It may just like to recover partition table by scanning cylinder data in hard disk.
Any idea? Thanks a lot.

Davis


  > >On Wed, Jul 27, 2005 at 11:33:05AM -0500, Jonathan E Brassow wrote:
  > >>I'm not familiar exactly with how the metadata gets laid on disk, but
  > >>I would think you could just 'vgcreate vg_name /dev/hdd2' (you did 
  > >>this
  > >>already) then 'lvcreate -n <lvname> -l <max size> vg_name'...  This of
  > >>course assumes that the previous lv resided wholly on /dev/hdd2.  Then
  > >>try mounting the new lv and see what happens.
  > >
  > >Before you do that, try vgcfgrestore.
  > >
  > 
  > AJ, when he did the initial 'vgcreate' was part of the process to 
  > create a backup copy of the metadata?  If so, vgcfgrestore could work.  
  > But otherwise, I'm not sure were the old metadata would be stored, 
  > since this disk is from a different machine...  Seems odd to me that 
  > vgcreate would blow over the old vg if it knew about it.  If it did not 
  > know (or detect the old vg), how would it know to backup the metadata?

  Not sure, but if the reason the disk was moved was because a cpu went out, i'm
  assuming the old root fs is also on that disk - hoping so anyway ;)  If so,
  the old root fs can be mounted and /etc/lvm/archive can be checked for a valid
  copy of the metadata.  (Assuming root wasn't on lvm...)

  As to why vgcreate didn't recognize the old VG...that's very odd - not sure
  what went wrong there...

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