Slony-I is enterprise-level "master to multiple slaves"
replication system with cascading and failover.

The big picture for the development of Slony-I is to build 
a master-slave system that includes all features and
capabilities needed to replicate large databases to a
reasonably limited number of slave systems.

Slony-I is developed as a system for data centers and backup
sites, where the normal mode of operation is that all nodes
are available.

WWW: http://www.slony.org/