Running clvm causes snapshots to fail

Bug #605187 reported by Eric Psalmond on 2010-07-13
6
This bug affects 1 person
Affects Status Importance Assigned to Milestone
lvm2 (Ubuntu)
Undecided
Unassigned

Bug Description

Binary package hint: lvm2

While clvm is running, snapshots are not created properly.

--------
root@host02:~# lvcreate -s /dev/raid10/root -n rootSnapshot -p r -L 10G
  Logical volume "rootSnapshot" created
root@host02:~# mount /dev/raid10/rootSnapshot /mnt/snapshots/root -o ro
mount: you must specify the filesystem type
---------

The snapshot is created, but rather than being a snapshot of the 'root' volume, the data there is just random/garbage.

Now, I turn off clvm, and the snapshot is created successfully.

---------
root@host02:~# /etc/init.d/clvm stop
 * Deactivating VG :
   ...done.
 * Stopping Cluster LVM Daemon clvm
   ...done.
root@host02:~# lvcreate -s /dev/raid10/root -n rootSnapshot -p r -L 10G
  Logical volume "rootSnapshot" created
root@host02:~# mount /dev/raid10/rootSnapshot /mnt/snapshots/root -o ro
root@host02:~# ls /mnt/snapshots/root
bin dev initrd lost+found mnt root srv usr
boot etc lib media opt sbin sys var
debian-binary home lib64 memtest86+.bin proc selinux tmp
root@host02:~#
---------

No volume groups on the cluster have the "cluster" attribute set:

---------
root@host02:~# vgdisplay
  --- Volume group ---
  VG Name raid10
  System ID
  Format lvm2
  Metadata Areas 1
  Metadata Sequence No 60
  VG Access read/write
  VG Status resizable
  MAX LV 0
  Cur LV 7
  Open LV 6
  Max PV 0
  Cur PV 1
  Act PV 1
  VG Size 295.00 GiB
  PE Size 4.00 MiB
  Total PE 75519
  Alloc PE / Size 38400 / 150.00 GiB
  Free PE / Size 37119 / 145.00 GiB
  VG UUID AvB9gR-GWFk-S4jy-hzzi-8CY8-OyCo-Q759vQ
---------

When I try to create snapshots on a clustered VG, lvmcreate correctly tells me that it's not supported yet.

LVM version is 2.02.54-1ubuntu4 0
Kernel 2.6.32-22-server
LVM Configuration: 'locking_type = 3'
Ubuntu Release: 10.04 LTS

Expected result: Valid, readable snapshot created.
Actual result: Snapshot of random/empty extents created. (browsing the raw devices in hexedit confirms the data is different in the snapshot)

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