[linux-lvm] hardware snapshots: uuid issue

[gilles.massen at restena.lu]

Hello everyone,

Some time ago I had a problem accessing a hardware snapshot of an LVM2 
partition. The reason: different physical volumes having the same UUIDs. 
The advice I was given was to use the "pvchange --uuid" command, but I'm 
unable to use that command whitout making the PV unusable. 

What happens is this: the PV is there, it is found, but  becomes an 
"unknown" device. pvdisplay and pvdisplay <device> disagree somewhat, 
andit seems as if the old uuid is sticking around. vgscan or pvscan are of 
no use.

Now I have no idea what else to try... BTW, I also failed having two 
instances of LVM by setting LVM_SYSTEM_DIR: the second instance still 
finds the PVs of the first even...even with the appropriate filters.

Any ideas how to continue here? For the time beeing the hardware snapshots 
are not very useful...

Best,
Gilles


Example: initial pvdisplay:

  --- Physical volume ---
  PV Name               /dev/sdb1
  VG Name               vg-test
  PV Size               1020.00 MB / not usable 0
  Allocatable           yes (but full)
  PE Size (KByte)       4096
  Total PE              255
  Free PE               0
  Allocated PE          255
  PV UUID               v3Oknf-6Rqa-Gh72-k0GO-c3I6-eoKS-odPWVr

# pvchange -v --uuid /dev/sdb1
    Using physical volume(s) on command line
    Finding volume group of physical volume "/dev/sdb1"
    Archiving volume group "vg-test" metadata.
    Updating physical volume "/dev/sdb1"
    Creating volume group backup "/etc/lvm/backup/vg-test"
  Physical volume "/dev/sdb1" changed
  1 physical volume changed / 0 physical volumes not changed

#pvdisplay -v
    Scanning for physical volume names
  Couldn't find device with uuid 'GaTpFU-XgFz-HRH2-Mtyb-GI1f-4LN4-TOe8FK'.
  --- Physical volume ---
  PV Name               unknown device
  VG Name               vg-test
  PV Size               1020.00 MB / not usable 0
  Allocatable           yes (but full)
  PE Size (KByte)       4096
  Total PE              255
  Free PE               0
  Allocated PE          255
  PV UUID               GaTpFU-XgFz-HRH2-Mtyb-GI1f-4LN4-TOe8FK

or else:# pvdisplay -v /dev/sdb1
    Using physical volume(s) on command line
  Couldn't find device with uuid 'GaTpFU-XgFz-HRH2-Mtyb-GI1f-4LN4-TOe8FK'.
  Couldn't find all physical volumes for volume group vg-test.
  format_text: _vg_read failed to read VG vg-test
  Couldn't find device with uuid 'GaTpFU-XgFz-HRH2-Mtyb-GI1f-4LN4-TOe8FK'.
  Couldn't find all physical volumes for volume group vg-test.
  format_text: _vg_read failed to read VG vg-test
  --- NEW Physical volume ---
  PV Name               /dev/sdb1
  VG Name
  PV Size               1023.62 MB
  Allocatable           NO
  PE Size (KByte)       0
  Total PE              0
  Free PE               0
  Allocated PE          0
  PV UUID               v3Oknf-6Rqa-Gh72-k0GO-c3I6-eoKS-odPWVr

# pvscan -v
    Wiping cache of LVM-capable devices
    Wiping internal cache
    Walking through all physical volumes
  Couldn't find device with uuid 'GaTpFU-XgFz-HRH2-Mtyb-GI1f-4LN4-TOe8FK'.
  PV unknown device      VG vg-test   lvm2 [1020.00 MB / 0    free]
  PV /dev/cciss/c0d0p6   VG data-vg   lvm2 [8.00 GB / 0    free]
  Total: 2 [9.00 GB] / in use: 2 [9.00 GB] / in no VG: 0 [0   ]


--
RESTENA - DNS-LU
6, rue Coudenhove-Kalergi
L-1359 Luxembourg
tel: (+352) 424409
fax: (+352) 422473