Pacemaker is an open source high-availability cluster software developed as a collaborative effort between Red Hat and Novell. Pacemaker clustering ensures vital resources receive increased availability. In the event of a failure, Pacemaker detects and automatically recovers virtual machines (VMs), applications and application-level features. The software then determines an optimal location for the service, based on cluster constraints. Pacemaker also supports redundancy configurations.
The software requires at least two Linux servers, but supports multiple deployment scenarios, from 2-node standby clusters to 16-node active/active configurations. Pacemaker also allows several active/passive clusters to be combined and to share a common backup node, which can reduce hardware costs.
Pacemaker is considered a de facto standard for Linux high availability (HA).