DRBD (Distributed Redundant Block Device) is a distributed storage subsystem for the Linux platform. DRBD is commonly used as a network based RAID 1 (mirroring) solution as part of a High Availability (HA) cluster, however it also provides support for active-active configurations when used with cluster aware filesystems such as GFS and OCFS2. DRBD enables businesses to accomplish their High Availability or Disaster Recovery goals with a significantly greater level of flexibility than proprietary alternatives.

The Linux-HA (High-Availability Linux) project provides a high-availability (clustering) solution for Linux, FreeBSD, OpenBSD, Solaris and Mac OS X which promotes reliability, availability, and serviceability (RAS). The project's main software product is Heartbeat, a GPL-licensed portable cluster management program for high-availability clustering. Heartbeat is a daemon that provides cluster infrastructure (communication and membership) services to its clients. This allows clients to know about the presence of peer processes on other machines and to easily exchange messages with them. In order to be useful to users, the Heartbeat daemon needs to be combined with a cluster resource manager (CRM) which has the task of starting and stopping the services (IP addresses, web servers, etc.) that the cluster will make highly available. Pacemaker is the preferred CRM for clusters based on Heartbeat.

Pacemaker is an Open Source, High Availability resource manager suitable for both small and large clusters. Hardware and application failures can result in prolonged downtime. If a failure occurs resource managers like Pacemaker automatically initiate recovery and make sure your application is available from one of the remaining machines in the cluster.