There are several classes of resource agents supported by Red Hat High Availability Add-On:
LSB — The Linux Standards Base agent abstracts the compliant services supported by the LSB, namely those services in
/etc/init.d and the associated return codes for successful and failed service states (started, stopped, running status).
OCF — The Open Cluster Framework is superset of the LSB (Linux Standards Base) that sets standards for the creation and execution of server initialization scripts, input parameters for the scripts using environment variables, and more.
systemd — The newest system services manager for Linux based systems, systemd uses sets of unit files rather than initialization scripts as does LSB and OCF. These units can be manually created by administrators or can even be created and managed by services themselves. Pacemaker manages these units in a similar way that it manages OCF or LSB init scripts.
Upstart — Much like systemd, Upstart is an alternative system initialization manager for Linux. Upstart uses jobs, as opposed to units in systemd or init scripts.
STONITH — A resource agent exclusively for fencing services and fence agents using STONITH.
Nagios — Agents that abstract plug-ins for the Nagios system and infrastructure monitoring tool.