SLVM Online Volume Reconfiguration (September 2009)

Physical volume groups and the lvmpvg file
The physical volume groups work exactly the same way regardless of the activation mode of the
volume group. In particular, you can use physical volume groups for configuration operations
(lvextend) on shared volume groups.
The /etc/lvmpvg file is not distributed across nodes automatically. The vgextend command acting
on a shared volume group updates only the local /etc/lvmpvg file. This is identical to a standalone
activation. The /etc/lvmpvg file is not automatically updated on the client nodes sharing the
volume group.
Online disk replacement
The method to replace disks is not changed. See the LVM Online Disk Replacement (LVM OLR)
whitepaper at http://docs.hp.com
.
Troubleshooting
When a configuration command issued on a shared volume group fails, the failure might be caused
by any node sharing the volume group or might be caused by several nodes.
The message displayed by the LVM configuration command (issued on the server node) might
correspond to a failure on another node. To determine exactly which nodes failed, see the system log
file.
In the system log file, the first line indicates the volume group on which the configuration failed,
followed by one line per node reporting an error. Nodes are identified by their hostname followed by
their node id in the HP Serviceguard cluster.
Example 1
In this example, the failure is because the lvmpud daemon is not started on one node sharing the
volume group.
On node2:
# lvcreate -M y -m 1 -l 10 vg_bigmir
lvcreate: The logical volume "/dev/vg_bigmir/lvol1" could not be created
as a special file in the file-system:
No such process
In /var/adm/syslog/syslog.log:
Jun 29 17:04:02 node2 vmunix: LVM: VG 128 0x005000: the distributed
configuration failed 13 0 0 204.
Jun 29 17:04:02 node2 vmunix: LVM: lvmpud timed out on node node3 2
If the lvmpud daemon is not started on any one of the nodes sharing the volume group and the
configuration change needs the services of the daemon, the configuration command fails with a No
such process message and a lvmpud timed out message is displayed in the system log file. In
the example, lvmpud was not started on the node node3.
Example 2
To generate an error for this example, the volume group directory was intentionally corrupted on the
node node4 before starting the test. This test attempts to create the logical volume lvol1 in the
volume group vg_bigmir. Normally, before creating the logical volume lvol1, no lvol1 file must
be present in /dev/vg_bigmir. To generate the error, before starting the test, a text file
/dev/vg_bigmir/lvol1 is manually created on node4. Then, when lvcreate tries to create the
device special file /dev/vg_bigmir/lvol1, it fails because it sees that there is already an
unexpected file /dev/vg_bigmir/lvol1 on node4.