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 that is 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 is localized by that messaging engine. All messaging workload for that destination are handled by that messaging engine; the workload cannot be shared. The availability characteristics of the destination are 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, the destination is localized by all the messaging engines in the cluster and the destination becomes partitioned across the messaging engines. The messaging engines share all traffic passing through the destination, which reduces the impact of one messaging engine failing. The availability characteristics of each destination partition are the same as the availability characteristics of the messaging engine that the partition is localized by.
You control the availability behavior of each messaging engine by modifying the core group policy that the HAManager applies to the messaging engine's HAGroup. See Policies for service integration for more information.