SLVM Single-Node Online Reconfiguration (SLVM SNOR)

Procedures
Making a configuration change in an active shared volume group
1. Identify the shared volume group on which a configuration change is required. Call
it vg_shared.
2. Identify one node of the cluster which is running an application (say SGeRAC)
using the shared volume group. Call it node1. The applications using the volume
group, vg_shared, on this node will remain unaffected during the procedure. The
cluster application, SGeRAC, needs to be scaled down to the single cluster node
node1.
3. Deactivate the volume group on all other nodes of the cluster, except node1, using
the "-n" option to the vgchange command.
vgchange -a n vg_shared
Ensure the volume group, vg_shared, is now active only on a single cluster node,
node1 by using the vgdisplay command on all cluster nodes. The "Status" should
show available on a single node only.
4. Change the activation mode to exclusive on node1
vgchange -a e -x vg_shared
Note: Ensure that none of the mirrored logical volumes in this volume group have
Consistency Recovery set to MWC (refer to lvdisplay(1M)). Changing the
activation mode back to shared will not be allowed in that case, since Mirror Write
Cache consistency recovery (MWC) is not valid in volume groups activated in
shared mode.
5. Make the desired configuration change on the volume group.
On node1, run the required command to change the configuration. For example,
lvextend -m 2 /dev/vg_shared/lvol1
Warning: If lvsplit is run on the logical volumes of a volume group in exclusive
mode, then changing the mode to shared would result in discarding the bit map used
for the subsequent fast lvmerge operation. In the absence of the bit map, an lvmerge
operation causes the entire logical volume to be resynchronized (refer to lvsplit(1M),
lvmerge(1M)).