A Sample Minimum Scenario - Novell LINUX ENTERPRISE SERVER 10 - INSTALLATION AND ADMINISTRATION 04-08-2006 Installation Manual

12.2 A Sample Minimum Scenario

The procedures within a two-node cluster when one node fails and the various types of
standby systems that can take over as necessary are outlined below (see Figure 12.1,
"A Simple High Availability Cluster" (page 271)).
Figure 12.1 A Simple High Availability Cluster
SAN
Primary Secondary
Interruption
Migrated data
Client application
The two servers (primary and backup) are both connected to a SAN (storage area net-
work). Depending on the mode, this is only accessed by the active node. The servers
communicate with each other in such a way that they regularly emit a "sign of life"
(heartbeat). The communication channels (or heartbeat links) are also laid out in a re-
dundant way, so independent channels can be used by means of a variety of network
cards and cable channels. If one of the links fails, its backups continue to report correctly
that the relevant server is still "alive". If there is no sign of life from the main system,
the standby system is activated, so it takes over the services of the failed partner and
removes it from the network completely (STONITH).
High Availability under Linux 271