The aim of a Real time Application Cluster (RAC) is to provide the availability of specific services within a system landscape. This is reached by reducing downtimes using redundant cluster nodes. A common RAC setup consists of two cluster nodes, which is the minimum for redundancy. If one server node crashes, the second node takes over the clustered services and secures the availability this way. This is also called a "two-node cluster" or a "failover cluster." According to the demands of availability, the number of server nodes can be increased to minimize the risks of failure of a node.
Design and Plan
Installing cluster software and integrating the services
Testing failover methodologies