The Red Hat Cluster Manager software was originally based on the open source Kimberlite http://oss.missioncriticallinux.com/kimberlite/ cluster project which was developed by Mission Critical Linux, Inc.
Subsequent to its inception based on Kimberlite, developers at Red Hat have made a large number of enhancements and modifications. The following is a non-comprehensive list highlighting some of these enhancements.
Packaging and integration into the Red Hat installation paradigm in order to simplify the end user's experience.
Addition of support for high availability NFS services.
Addition of support for high availability Samba services.
Addition of support for using watchdog timers as a data integrity provision
Addition of service monitoring which will automatically restart a failed application.
Rewrite of the service manager to facilitate additional cluster-wide operations.
Addition of the Red Hat Cluster Manager GUI, a graphical monitoring tool.
A set of miscellaneous bug fixes.
The Red Hat Cluster Manager software incorporates STONITH compliant power switch modules from the Linux-HA project http://www.linux-ha.org/stonith/.