How-To Manage the Cluster ?

• Migrate a VM to the secondary node

gnt-instance migrate <vm>

• Migrate the secondary disk to another node

gnt-instance replace-disks -n <newnode> <vm>

• Cluster's Health verification

gnt-cluster verify-disk
gnt-cluster verify

• Migrate all the VM of a node & flag it offline

gnt-node migrate <node>
gnt-node failover <node>
# flag the node "offline"
gnt-node modify -C no -O yes <node>

• Change VM parameters

gnt-instance modify --backend-parameters=vcpus=4 <vm>
gnt-instance modify -B memory=4096M <vm>

• Extend a VM's disk

gnt-instance grow-disk <vm> <disk-number> <size-to-grow>
gnt-instance reboot <vm>

On the VM :

fdisk /dev/xvda (in my case)
p # List and note starting partition number
d # Delete the partition
n # New partition with same number and starting number
w # Write
reboot
pvresize /dev/xvda1
lvextend -L+<size-in-giga> /dev/vg<vm>/<lv-to-extend>
resize2fs /dev/vg<vm>/<lv-to-extend>