Novell OPEN ENTERPRISE SERVER CLUSTER SERVICES 1.8.2 - ADMINISTRATION Manual page 10

Shared disk fault tolerance can be obtained by implementing RAID on the shared disk subsystem.
An example of the benefits Novell Cluster Services provides can be better understood through the
following 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 is 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
Web Site A
Web Site B
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 depending on Web
Server 1 for Internet access, e-mail, and information lose their connections. The following figure
shows how resources are moved when Web Server 1 fails.
Figure 1-2
Web Server 1
10 OES Novell Cluster Services 1.8.2 Administration Guide for Linux
Data protection
Server Consolidation
Storage Consolidation
Three-Server Cluster
Web Server 1
Web Site C
Web Site D
Fibre Channel Switch
Three-Server Cluster after One Server Fails
Web Server 2
Web Site A
Web Site C
Web Site D
Fibre Channel Switch
Web Server 2
Web Site E
Web Site F
Web Server 3
Web Site B
Web Site E
Web Site F
Shared Disk
System
Web Server 3