Linux-HA heartbeat

Heartbeat is a daemon that provides cluster infrastructure
(communication and membership) services to its clients. This allows
clients to know about the presence (or disappearance!) of peer
processes on other machines and to easily exchange messages with them.

Heartbeat still comes with an integrated primitive resource
manager, which basically is just a shell script.  This is also
referred to as "v1 style" or "haresources style" configuration.

You might also want to install cluster-glue, heartbeat, resource-agents,
fence-agents.