1.2. High Availability Add-On Introduction

The High Availability Add-On is an integrated set of software components that can be deployed in a variety of configurations to suit your needs for performance, high availability, load balancing, scalability, file sharing, and economy.

The High Availability Add-On consists of the following major components:

Cluster infrastructure — Provides fundamental functions for nodes to work together as a cluster: configuration-file management, membership management, lock management, and fencing.
High availability Service Management — Provides failover of services from one cluster node to another in case a node becomes inoperative.
Cluster administration tools — Configuration and management tools for setting up, configuring, and managing a the High Availability Add-On. The tools are for use with the Cluster Infrastructure components, the high availability and Service Management components, and storage.

Note

Only single site clusters are fully supported at this time. Clusters spread across multiple physical locations are not formally supported. For more details and to discuss multi-site clusters, please speak to your Red Hat sales or support representative.

You can supplement the High Availability Add-On with the following components:

Red Hat GFS2 (Global File System 2) — Part of the Resilient Storage Add-On, this provides a cluster file system for use with the High Availability Add-On. GFS2 allows multiple nodes to share storage at a block level as if the storage were connected locally to each cluster node. GFS2 cluster file system requires a cluster infrastructure.
Cluster Logical Volume Manager (CLVM) — Part of the Resilient Storage Add-On, this provides volume management of cluster storage. CLVM support also requires cluster infrastructure.
Load Balancer Add-On — Routing software that provides IP-Load-balancing. the Load Balancer Add-On runs in a pair of redundant virtual servers that distributes client requests evenly to real servers that are behind the virtual servers.