Siebel Server Installation Guide for Microsoft Windows > Clustering Your Siebel Deployment for Failover > About Clustered Servers >

Clustering Strategies

You may run the same application on two nodes, using one as the active and the other as the backup, or different applications on individual nodes, as described in the following sections.

Active-Active Configuration

In an active-active configuration, both nodes in the cluster are used. Each of them may host different instances of the same application or different applications. For example, the Siebel Database may run on one node and a Siebel Server on another, or the Siebel Gateway may run on one node and a Siebel Server on the other node.

Alternatively, one active node can host a production server and another active node can host a development or testing server. When a failover occurs, the production node fails over to the development or testing node. The development or testing environments on the secondary node are stopped and the production services are given priority.

Active-Passive Configuration

An active-passive configuration is one in which only one node is being used to host application. The other one is idled and serves as a hot backup. One of two clustered nodes acts as a standby that remains idle (passive) until a failure occurs in the active node. In this case, the previously running applications would come back on line when the passive node became active.

Choosing the Right Strategy

Both active-active and active-passive clusters are valid solutions. The main
trade-offs between the two configurations are cost and performance of the active server after a failover.

Active-active clusters use all the hardware on a continuous basis, thereby offering a better return on investment. Should a failover occur, the load from the failed server would be added to the already existing load on the surviving server with the effect of overloading it and potentially degrading the performance of all applications on that server.

However, because failovers should be very infrequent and should last only a short time, this degradation is, in practice, often acceptable. Therefore, servers are often deployed on active-active clusters.

Active-passive clusters require a standby server that is used only in exceptional circumstances (failovers). Therefore, these incur additional hardware cost without providing additional capacity. The benefit of active-passive clusters lies in the fact that, even after a failover, the same level of hardware resources are available for each application, thereby eliminating any performance impact to the application. This is particularly important for performance-critical areas such as the database. In fact, the most common use of active-passive clusters is for database servers.

 Siebel Server Installation Guide for Microsoft Windows 
 Published: 25 June 2003