System state
The state of the clustered system holds all of the configuration and internal data. The system state information is held in volatile memory.
If the power to a node fails and a backup power source is not
available, the system state information is lost which can result in data loss. To avoid loss of
data, ensure that each node is powered by an uninterrupted power source (UPS). If mainline power
fails, the UPS provides power and time for you to issue the svctask stopsystem command, answer "yes" to accept the confirmation
message, and start the system shutdown process. As the system shuts down, the node loses access
to volumes; however, data is not lost. While the UPS supplies power, the node writes cache data and
the configuration information that is held in memory to its boot drive. The UPS for the
node must be able to provide enough power to allow the shutdown process to complete.
Attention: System data might be lost if you do not issue the svctask stopsystem command and accept the
confirmation message to shut down the system (or create an external system to issue the command
automatically) or if the node does not have enough power to complete the shut-down process.
Figure 1 shows an example of a system that contains four nodes. Node 1 is elected as the configuration node. The configuration node can be thought of as the node 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 nodes. This state-driven model of clustering ensures that all nodes in the system know and maintain the exact system state at any time.
Figure 1. Clustered system, nodes, and system
state