Cluster Configurations

Cluster configurations with the High Availability Extension might or might not include a shared disk subsystem. The shared disk subsystem can be connected via high-speed Fibre Channel cards, cables, and switches, or it can be configured to use iSCSI. If a server fails, another designated server in the cluster automatically mounts the shared disk directories previously mounted on the failed server. This gives network users continuous access to the directories on the shared disk subsystem.

	Shared Disk Subsystem with cLVM
When using a shared disk subsystem with cLVM, that subsystem must be connected to all servers in the cluster from which it needs to be accessed.

Typical resources might include data, applications, and services. The following figure shows how a typical Fibre Channel cluster configuration might look.

Figure 1.3. Typical Fibre Channel Cluster Configuration

Although Fibre Channel provides the best performance, you can also configure your cluster to use iSCSI. iSCSI is an alternative to Fibre Channel that can be used to create a low-cost Storage Area Network (SAN). The following figure shows how a typical iSCSI cluster configuration might look.

Figure 1.4. Typical iSCSI Cluster Configuration

Although most clusters include a shared disk subsystem, it is also possible to create a cluster without a share disk subsystem. The following figure shows how a cluster without a shared disk subsystem might look.

Figure 1.5. Typical Cluster Configuration Without Shared Storage