Dell PowerConnect W Clearpass 100 Software 3.7 Deployment Guide - Page 347
High Availability Services, Accessing High Availability, About High Availability Systems
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Chapter 10 High Availability Services The goal of a highly available system is to continue to provide network services even if a hardware failure occurs. High Availability Services provides the tools required to achieve this goal. These tools include service clustering, fault tolerance, database replication, configuration replication, automatic failover and automatic recovery. You must have two Amigopod Visitor Management Appliance servers that have the High Availability Services plugin installed in order to use these features. See "About High Availability Systems" in this chapter for an introduction to High Availability Services including a detailed explanation of how it works. See "Cluster Status" in this chapter for an explanation of the cluster status messages. See "Recovering From a Failure" in this chapter for the procedures to use if you need to recover a failed cluster. Accessing High Availability Use the High Availability command link available from the Administrator start page to access the clustering and replication features. Alternatively, use the High Availability navigation menu to jump directly to any of the high availability features. About High Availability Systems Terminology & Concepts A cluster consists of a primary node and a secondary node, configured so that a failure of either node will not prevent the cluster as a whole from performing its normal functions. The primary node is the active server in a cluster. The cluster's network services are always delivered by the primary node. The secondary node is the backup server in a cluster. If the primary node fails, the secondary automatically takes over and continues delivering network service. Fault tolerance is the ability of a server cluster to continue operating if either the primary or secondary node experiences a hardware failure. Failover is the process by which the secondary node assumes control of the cluster once the primary node has failed. Amigopod 3.7 | Deployment Guide High Availability Services | 347