High-availability (HA) clustering is a solution that uses clustering software and special purpose hardware to minimize system downtime. HA clusters are groups of computing resources that are implemented to provide high availability of software and hardware computing services. HA clusters operate by having redundant groups of resources (such as CPU, disk storage, network connections, and software applications) that provide service when the primary system resources fail. webMethods Broker can run in an HA cluster environment, under Windows or UNIX.

In a clustered environment, groups of resources (such as CPU, disk storage, network connections, and software applications) are connected to shared storage hardware, and controlling cluster software. When the primary system fails, the cluster software switches control to a secondary group of resources.

Without an HA cluster, a failed resource will remain unavailable until that resource is brought back online. Based on the dependencies among resources, a failed resource can make the entire computing environment unusable. HA clustering remedies this problem by detecting hardware or software failures and immediately starting (or failing over to) the redundant resources on another node without requiring administrative intervention. As part of this failover process, clustering software will start the resources on the redundant node in a predefined order (or resource dependency) to ensure that the entire node will come up properly.