Clustering over a wide area network
A cluster over a wide are network (WAN) works the same way as a cluster on a LAN. However, if you have a low-speed WAN, you should consider disabling cluster replication. Instead, use scheduled replication more frequently than usual, such as every hour. This reduces WAN traffic, bottlenecks, and the cost of continual transmission.
IBM® Domino® fails over to the most available server in the cluster, not necessarily the physically closest server. For example, if you have three servers -- one in Boston, one in New York, and one in Hong Kong -- the Boston server would fail over to the Hong Kong server if it is more available than the New York server. You can control this behavior to some extent, and limit the workload of a server, by changing the server availability thresholds on the cluster servers.
Using a cluster over a WAN is a good idea for disaster planning. Having emergency backup servers at different locations is a good way to ensure that necessary data is always available when you need it.