Using active or passive state varyon in PowerHA SystemMirror
PowerHA® SystemMirror® detects when a volume group included in a shared resource group is converted to or defined as an enhanced concurrent mode volume group, and notifies the LVM which node currently owns the volume group.
Based on this information, the LVM activates the volume group in the appropriate active or passive state depending on the node on which this operation takes place:
- Upon cluster startup, if the volume group resides currently on the node that owns the resource group, PowerHA SystemMirror activates the volume group on this node in active state. PowerHA SystemMirror activates the volume group in passive state on all other nodes in the cluster. Note that PowerHA SystemMirror will activate a volume group in active state only on one node at a time.
- Upon fallover, if a node releases a resource group, or, if the resource group is being moved to another node for any other reason, PowerHA SystemMirror switches the varyon state for the volume group from active to passive on the node that releases the resource group (if cluster services are still running), and activates the volume group in active state on the node that acquires the resource group. The volume group remains in passive state on all other nodes in the cluster.
- Upon node reintegration, this procedure is repeated. PowerHA SystemMirror changes the varyon state of the volume group from active to passive on the node that releases the resource group and varies on the volume group in active state on the joining node. While activating, the volume group remains passive on all other nodes in the cluster.
Note: The switch between active and passive states is necessary to
prevent mounting file systems on more than one node at a time.