Pacemaker

Project History
Pacemaker came to life in late 2003 when Lars convinced SUSE to hire me to implement a new cluster resource manager for Heartbeat. Although simple to configure, the old version 1 cluster manager had four key deficiencies
 * Maximum of 2-nodes
 * Highly coupled design and implementation
 * Overly simplistic group-based resource model
 * Inability to detect and recover from resource-level failures

Then, year and a half later, on Saturday July 30 (2005), Heartbeat 2.0.0 was released containing the first public version of the CRM.

After many successful releases, the decision was made at the end of 2007 to spin-off the CRM into its own project after the 2.1.3 Heartbeat release in order to
 * support both the OpenAIS and Heartbeat cluster stacks equally
 * decouple the release cycles of two projects at very different stages of their life-cycles
 * foster clearer package boundaries, thus leading to
 * better and more stable interfaces

This transition was completed on January 16, 2008 with the 0.6.0 release of Pacemaker which was the first to support both cluster stacks. The (feature frozen) 0.6 stable series is derived from, and fully compatible with, the 2.1.3 CRM and will receive bug-fix-only updates throughout the rest of 2008 and early 2009.

The current Pacemaker stable series is 1.0 and contains many improvements over prior releases, including:
 * A more intuitive syntax
 * Failure (migration) thresholds and timeouts
 * Tool for making offline configuration changes
 * A unified command line configuration tool that hides the underlying xml
 * Rules, instance_attributes, meta_attributes and sets of operations can be deﬁned once and referenced in multiple places
 * The ability to connect to the CIB from non-cluster machines
 * Allow recurring actions to be triggered at known times
 * A more powerful RelaxNG-based configuration schema