7.1 Clustering WebSphere for availability
"Clustering" is a fundamental approach for accomplishing high availability. IBM WAS Network Deployment V6 offers a built-in application server clustering function and the HAManager for protecting WebSphere singleton services. Clustering application servers provides workload management and failover for applications that reside on the application server cluster. It is also possible to use external clustering software such as HACMP to provide availability clustering for WAS.
These two kinds of cluster failovers can be categorized as follows:
IP-based cluster failover, using the IBM High Availability Cluster Multi-Processing for AIX 5L (HACMP) Non-IP cluster failover, such as WLM and HAManager.
Usually, IP-based cluster failover is slower (taking one to five minutes), and non-IP cluster failover is very fast (instantaneous). WebSphere V6 HAManager does not require extra software. However, IP cluster failover still relies on cluster software such as HACMP to provide the cluster information.