Re: [linux-lvm] How to restore a PV ??

[Brian McCullough <bdmc@bdmcc-us.com>]

I am having a similar problem with a drive that was created under LVM
version 1.  More questions below.


On Mon, Oct 16, 2006 at 02:20:14PM -0500, Jonathan E Brassow wrote:
> On each disk in the volume group is a record of the changes that have 
> been made to the volume group.  The last item in the record is the 
> current lvm meta-data.  If you can retrieve that, it is the same as 
> having the backup file which would normally be found in 
> /etc/lvm/backup.
> 
> You could use hexdump, but I find it much simpler to use 'less -f 
> <device>'.  You should see something like:
> 
> <crap>
> principal {
> ...
> }
> <comments>
> <crap>
> principal {
> ...
> }
> <comments>
> <crap>


Is this also true for LVM1?  I have examined the disk ( there are 5 LVs
on this disk, one elsewhere ( nowhere! ) ) and it doesn't seem to follow
this format.

If this is not true, is there any way to recover such a Volume Group?

Here is what vgscan and pvscan show:

[root@clachan media]# pvscan
  5 PV(s) found for VG vg_system: expected 6
  Logical volume (lvol4) contains an incomplete mapping table.
  PV segment VG free_count mismatch: 1381 != 2572
  PV segment VG extent_count mismatch: 1417 != 2608
  Internal error: PV segments corrupted in vg_system.
[root@clachan media]# vgscan
  Reading all physical volumes.  This may take a while...
  5 PV(s) found for VG vg_system: expected 6
  5 PV(s) found for VG vg_system: expected 6
  Volume group "vg_system" not found
[root@clachan media]# vgchange -a y --partial vg_system
  Partial mode. Incomplete volume groups will be activated read-only.
  5 PV(s) found for VG vg_system: expected 6
  Logical volume (lvol4) contains an incomplete mapping table.
  PV segment VG free_count mismatch: 1381 != 2572
  PV segment VG extent_count mismatch: 1417 != 2608
  Internal error: PV segments corrupted in vg_system.
  Unable to find volume group "vg_system"


I do have several copies of the config file, also on this drive ( in a
real ext2 partition! ).  Could I just edit the file to remove lvol4 (
with 250 segments! ) and do a vgcfgrestore from an LVM2 system?


Thank you,
Brian