You can add either a server or a cluster to a service integration bus, to create either a server bus member or a cluster bus member.
A cluster deployment can provide workload sharing, availability, or both, depending on the number of messaging engines in the cluster and the policy bound to each messaging engine's HAGroup.
If there is only one messaging engine in the cluster and you deploy a destination to the same cluster, the destination will be localized by that messaging engine. The destination will not be partitioned and all messaging workload for that destination will be handled by that messaging engine; it cannot be shared. The availability characteristics of the destination will be the same as the availability characteristics of the messaging engine.
You can benefit from increased scalability by introducing additional messaging engines to the cluster. When you deploy a destination to the cluster it will be localized by all the messaging engines within the cluster and the destination will become partitioned across the messaging engines. The messaging engines will now share all traffic passing through the destination, reducing the impact of one messaging engine failing. The availability characteristics of each destination partition will be the same as the availability characteristics of the messaging engine the partition is localized by.
You control the availability behavior of each messaging engine by modifying the policy that the HAManager applies to the messaging engine's HAGroup. See Policies for service integration for more information.