An EAServer cluster is a group of servers that share replicated repository information to run the same components and Web applications. A clustered deployment provides load balancing and high availability, at the cost of slightly increased overhead to replicate client session information between servers in the cluster. If you are not familiar with these concepts, see these chapters in the EAServer System Administration Guide:
If your application cannot support the required number of clients running on one machine, moving to a cluster allows EAServer to balance the load across several machines. Depending on the hardware you choose, a cluster of low priced machines may be less expensive than upgrading to a single machine with multiple CPUs. Clusters also provide failover support when you run servers on multiple machines: no single machine failure takes your application offline.
Clusters incur a slight overhead increase due to the need to replicate client session data between servers. You can minimize the performance impact by minimizing your use of stateful components and HTTP session storage, and by tuning the state replication mechanisms.
