More than one subsystem can be configured in an installation of Certificate System. There can be multiple instances of a type of subsystem on a host or across different hosts. For failover support, one configuration option is to duplicate, or clone, an instance so that more than one instance has the same configuration information. Clones and masters share the same set of keys and certificates. Cloned CAs issue certificates with the same issuer name and keys, but use different sets of serial numbers. A master and clone function essentially as a single server with failover support. This can also be used for load balancing for high-traffic subsystems. For details about cloning a subsystem, see Chapter 21, Configuring the Certificate System for High Availability.