heartbeat 是可以从 Linux-HA 项目 Web 站点公开获得的软件包之一。它提供了所有 HA 系统所需要的基本功能，比如启动和停止资源、监测群集中系统的可用性、在群集中的节点间转移共享 IP 地址的所有者等。它通过串行线、以太网接口或者同时使用二者来监测特定服务（或多个服务）的健康状况。当前版本支持两节点配置，使用专门的 heartbeat“pings”来检查服务的状态和可用性。heartbeat 为比本文中所描述的更复杂的情形提供了基础，比如 active/active 配置，该配置中两个节点是并行工作的，负责完成负载平衡。
Heartbeat is a daemon that provides cluster infrastructure (communication and membership) services to its clients. This allows clients to know about the presence (or disappearance!) 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 cluster will make highly available. Pacemaker is the preferred cluster resource manager for clusters based on Heartbeat.
The basic goal of the High Availability Linux project is to:
Provide a high-availability (clustering) solution for Linux which promotes reliability, availability, and serviceability (RAS) through a community development effort.
The Linux-HA project is a widely used and important component in many interesting High-Availability solutions. We estimate that we currently have around thirty thousand installations up in mission-critical uses in the real world since it became suitable for mission critical production in 1999. Interest in this project continues to grow. These web pages are average more than 17000 hits per day, and we see around 100 downloads of our software per day.
Heartbeat now ships as part of SUSE Linux, Mandriva Linux, MSC Linux, Debian GNU/Linux, Ubuntu Linux, Red Flag Linux, and Gentoo Linux. Ultra Monkey, and several company s embedded systems are also based on it. Although this is called the Linux-HA project, the software is highly portable and runs on FreeBSD and Solaris as well (even MacOS X from time to time).