Clusters can improve the resilience and capacity of the Messaging system by allowing multiple servers that perform the application role to act together. You can combine up to three application servers to form a cluster and add a fourth server for redundancy as long as the active traffic does not exceed 300 ports. You can use a maximum of four application servers per system.
Clustering also replicates user data, such as passwords and greetings, in real time to ensure seamless service between each member in the cluster. However, updates to application roles within other clusters occur only at the time of the nightly maintenance routine.
Clusters are typically designed based on physical location and each application role is configured identically. If you want to retrieve messages when either the storage role or mailbox store is unavailable, a member of a cluster combines a list of available messages from the other servers within the cluster.
Starting with Avaya Aura® Messaging 6.1 and later, members of a cluster regularly test connectivity with other members of the same cluster so that if one member becomes unavailable, prolonged delays are not encountered when trying to obtain a message from another server.
You can have multiple clusters within a system as long as the system maximum port capacity of 300 is maintained.