[linux-lvm] Re: Problem with vgscan "only found 626 of 625 LEs for LV"

[Andreas Dilger]

On Sep 11, 2001  11:30 +0000, Tomas Edwardsson wrote:
> I had already tried the vgcfgrestore, it didn't seem to help but I discovered
> that the UUID for one of my PVs was missing so I ran the uuid-fixer and now
> they all have UUIDs again (don't know if that is relevant). 
> 
> I have run the pvdata on all my PVs although I think the right one is the
> following file run with pvdata -avP /dev/hdd1:
>   http://vefur.hp.is/lvm/pvdata-hdd1.txt

Yes, this clearly shows that lvol1 has 625 LEs (in the LV data), but it
has PE 0-625 from that PV assigned to it (total of 626 PEs).  I don't
know which one is correct, nor how it got that way.  If you have a
filesystem on that LV, you could find out how big the fs is to figure
out which value needs fixing.  For ext2, you can do:

dumpe2fs -h /dev/vg00/lvol1

and figure out if it is 2500MB (625 LE) or 2504MB (626LE).  Then (the fun
part) you need to go and edit either the LV table or the PE table to have
the right numbers in it.  I'm guessing the LV table is wrong (and even if
not, it is safer to add the PE to the end than to truncate your filesystem).

dd if=/dev/hdd1 of=/hdd.sav bs=1024 count=188		# backup LVM metadata
dd if=/dev/hdd1 of=/lv1.dat bs=1 skip=43008 count=328	# get lvol1 metadata
od -Ad -tx1 /lv1.dat					# show lvol1 metadata

# 625 = 0x271 which you should see at offset 300, 301 of the LV struct
# 626 = 0x272 = 0x02 0x72, 0x72 = "r" in ASCII, so we write this into LV
echo "r" | dd of=/lv1.dat count=1 seek=300		# write 0x72 to LE count

od -Ad -tx1 /lv1.dat					# show lvol1 metadata
# we should now see 0x72 0x02 0x00 0x00 at offset 300 of the LV metadata

dd if=/lv1.dat of=/dev/hdd1 bs=1 seek=43008		# write LV meta to disk
pvdata -avP /dev/hdd1					# verify all is well
vgscan							# should be OK now

Cheers, Andreas
-- 
Andreas Dilger  \ "If a man ate a pound of pasta and a pound of antipasto,
                 \  would they cancel out, leaving him still hungry?"
http://www-mddsp.enel.ucalgary.ca/People/adilger/               -- Dogbert