heartbeat is a sophisticated multinode resource manager for High
Availability clusters.

It can failover arbitrary resources, ranging from IP addresses over NFS
to databases that are tied in via resource scripts. The resources can
have arbitrary dependencies for ordering or placement between them.

heartbeat contains a cluster membership layer, fencing, and local and
clusterwide resource management functionality.

1.2/1.0 based 2-node only configurations are supported in a legacy
mode.

heartbeat implements the following kinds of heartbeats:

- Serial ports

- UDP/IPv4 broadcast, multi-cast, and unicast

- IPv4 "ping" pseudo-cluster members.