HP ProLiant 2500 Compaq ProLiant Cluster HA/F100 and HA/F200 Administrator Gui - Page 34

Designing the Compaq ProLiant Clusters HA/F100 and HA/F200 2-3 An active/active configuration has two primary designs: s The first design uses Microsoft Cluster Server (MSCS) failover capabilities on both nodes, enabling Node1 to fail over clustered applications to Node2 and enabling Node2 to fail over clustered applications to Node1. This design optimizes availability since both nodes can fail over applications to each other. s The second design is a one-way failover. For example, MSCS may be set up to allow Node1 to fail over clustered applications to Node2, but not to allow Node2 to fail over clustered applications to Node1. While this design increases availability, it does not maximize availability since failover is configured on only one node. When designing cluster nodes to fail over to each other, ensure that each server has enough capacity, memory, and processor power to run all applications (all applications running on the first node plus all clustered applications running on the other node). When designing your cluster so that only one node (Node1) fails over to the other (Node2), ensure that Node2 has enough capacity, memory, and CPU power to execute not only its own applications, but to run the clustered applications that can fail over from Node1. Another consideration when determining your servers' hardware is understanding your clustered applications' required level of performance when the cluster is in a degraded state (when one or more clustered applications is running on a secondary node). If Node2 is running near peak performance when the cluster is in a normal operating state, and if several clustered applications are failed over from Node1, Node2 will likely execute the clustered applications more slowly than when they were executed on Node1. Some level of performance degradation may be acceptable. Determining how much degradation is acceptable depends on the company.