Cluster Configurations - Novell SUSE LINUX ENTERPRISE SERVER 10 SP2 HEARTBEAT Manual

Now suppose the problems with Web Server 1 are resolved, and Web Server 1 is returned
to a normal operating state. Web Site A and Web Site B can either automatically fail
back (move back) to Web Server 1, or they can stay where they are. This is dependent
on how you configured the resources for them. There are advantages and disadvantages
to both alternatives. Migrating the services back to Web Server 1 will incur some down-
time. Heartbeat also allows you to defer the migration until a period when it will cause
little or no service interruption.
Heartbeat also provides resource migration capabilities. You can move applications,
Web sites, etc. to other servers in your cluster without waiting for a server to fail.
For example, you could have manually moved Web Site A or Web Site B from Web
Server 1 to either of the other servers in the cluster. You might want to do this to upgrade
or perform scheduled maintenance on Web Server 1, or just to increase performance
or accessibility of the Web sites.

1.3 Cluster Configurations

Heartbeat cluster configurations 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 direc-
tories on the shared disk subsystem.
IMPORTANT: Shared Disk Subsystem with EVMS
When using a shared disk subsystem with EVMS, that subsystem must be con-
nected to all servers in the cluster.
Typical Heartbeat resources might include data, applications, and services. The following
figure shows how a typical Fibre Channel cluster configuration might look.
Overview 5