SLVM Online Volume Reconfiguration (September 2009)

Commands that were already working on online shared volume groups continue to work as before.
For example, the display commands, lvsync.
The following commands are supported on a shared volume group Version 2.1 or higher. Before
MORE (introduced in the HP-UX 11i v3 September 2009 release), these commands fail on a shared
volume group.
• lvchange
• lvcreate
• lvmerge
• lvreduce
• lvremove
• lvsplit
• pvmove
• vgextend
• vgmodify
• vgmove
• vgreduce
lvmerge and lvsplit Behavior Change
After a mirrored logical volume has been split (lvsplit) on a shared volume group, a merge (lvmerge)
resynchronizes the whole logical volume instead of only the changed area. In other words, the "fast
merge" (available for standalone and exclusive activation) is not available for shared activation.
On which node do you issue the LVM commands?
When used on a shared Version 2.1 or higher volume group, you must issue the LVM configuration
commands listed previously on the server node. If they are issued on a client node, the following error
message is displayed:
The volume group vg_name is active as client in Shared Mode. Cannot
perform configuration change.
To determine which node is the server for the volume group, use the vgdisplay -v command. The
output lists the name of the nodes sharing the volume group qualified with "server" or "client".
Volume naming
Online configuration of a shared volume group requires the volume group name and logical volume
names to be the same across all the nodes sharing the volume group. You must not rename the LVM
volume device special files without also renaming them on the other nodes. When you create a
logical volume on a shared volume group, LVM distributes the name chosen by you to the other
nodes, insuring that all the nodes see the same logical volume name.
Which nodes in an HP Serviceguard cluster receive the changes?
A configuration change initiated by an LVM command on a shared volume group is distributed across
some nodes in the cluster. However, other nodes in the cluster might not receive the LVM configuration
change. This is because LVM distributes the change only to the nodes sharing the volume group. For
example, in a 10-node cluster, if the volume group is shared by only 4 nodes, only those 4 nodes
receive the LVM configuration change.
This behavior has the following effects:
• When using vgextend or vgreduce, the /etc/lvmtab_p file is automatically updated only on the
nodes sharing the volume group.