CLUSTERS

Examples of clustering hub servers
If you use a hub-and-spoke configuration, which is very efficient, you can cluster the hub servers to ensure availability. If one of the hub servers is not available, mail routing or replication fails over to another hub server.

The following figure shows two hub servers in a cluster. The purpose of this cluster is to route mail.

Clustering hub servers to route mail

When the primary purpose of the hub servers is replication, the previous configuration may not work well in some enterprises because of the amount of replication that is required. Because both hub servers need to contain the same databases, this configuration causes a lot of replication. Depending on the equipment you use, this configuration could slow down servers and create a lot of network traffic. If that is the case in your enterprise, you might consider using an active-passive operating system cluster for your hub servers, as in the following figure.

Clustering hub servers for replication