System state

If the mainline power fails, back up power to a node maintains internal power long enough for the system state information to be stored on the internal disk drive of each node. The write cache data and configuration information that is held in memory is stored on the internal disk drive of the node. If the partner node is still online, it attempts to flush the cache; the node then continues operation and its write cache is disabled.

Node 1 is elected as the configuration node. The configuration node can be thought of as the node canister that controls the updating of system state. If the configuration node fails, the system can elect a new node to take over its responsibilities. When a change is made to the configuration or internal system data, the same change is applied to all node canisters. This state-driven model of clustering ensures that all nodes in the system know and maintain the exact system state at any time.

1. A user request (1) is made that results in a change to the system configuration.
2. The configuration node, Node 1, controls the updates to the system state (2).
3. The configuration node then forwards that state change to all node canisters, including Node 1. All nodes then make the state change at the same time (3).