Novell LINUX ENTERPRISE 11 - HIGH AVAILABILITY, Manual, Page: 16 / 298

• Storage consolidation
Shared disk fault tolerance can be obtained by implementing RAID on the shared disk
subsystem.
The following scenario illustrates some of the benefits the High Availability Extension
can provide.
Example Cluster Scenario
Suppose you have configured a three-server cluster, with a Web server installed on
each of the three servers in the cluster. Each of the servers in the cluster hosts two Web
sites. All the data, graphics, and Web page content for each Web site are stored on a
shared disk subsystem connected to each of the servers in the cluster. The following
figure depicts how this setup might look.
Figure 1.1 Three-Server Cluster
During normal cluster operation, each server is in constant communication with the
other servers in the cluster and performs periodic polling of all registered resources to
detect failure.
Suppose Web Server 1 experiences hardware or software problems and the users de-
pending on Web Server 1 for Internet access, e-mail, and information lose their connec-
tions. The following figure shows how resources are moved when Web Server 1 fails.
6 High Availability Guide