Pacemaker is a Open Source, High Availability cluster. Pacemaker and in general Linux clustering have been around for a very long time. Both matured greatly over the past 10 to 15 years.Today Pacemaker is a very simple streamlined bundle that includes the Pacemker clustering, fencing agents, resource agents and the heartbeat (corrosync). Pacemaker is available in Red Hat Enterprise Linux 7 as the High Availability option. In this article I will provide an overview of Pacemaker and a tutorial on how to setup a two-node pacemaker cluster for Apache using shared storage.