1.1.3.4 High Availability

In addition to the software components in two tiers, the Access Anywhere design includes Sun Cluster software to provide high availability in case of hardware failure. Each cluster consists of two redundant nodes that run the same software components. Back-end clusters connect to the storage area network (SAN) which includes both redundant switches and redundant disks for fail-safe operation. For more information about the SAN architecture, see 2.2 Storage Area Network (SAN).

The EdgeMail example deploys 4 clusters running Messaging Server and 2 clusters running Calendar Server. System scalability is achieved by increasing the number of clusters according to user needs, which simply involves adding pairs of back-end hosts.