Red Hat Cluster for Enterprise Linux 5 Configuration page 20

Certain low-cost alternatives, such as host RAID controllers, software RAID without cluster
support, and multi-initiator parallel SCSI configurations are not compatible or appropriate for
use as shared cluster storage.
Data integrity assurance
To ensure data integrity, only one node can run a cluster service and access cluster-service
data at a time. The use of power switches in the cluster hardware configuration enables a
node to power-cycle another node before restarting that node's cluster services during a
failover process. This prevents two nodes from simultaneously accessing the same data
and corrupting it. It is strongly recommended that fence devices (hardware or software solu-
tions that remotely power, shutdown, and reboot cluster nodes) are used to guarantee data
integrity under all failure conditions. Watchdog timers provide an alternative way to to en-
sure correct operation of cluster service failover.
Ethernet channel bonding
Cluster quorum and node health is determined by communication of messages among
cluster nodes via Ethernet. In addition, cluster nodes use Ethernet for a variety of other crit-
ical cluster functions (for example, fencing). With Ethernet channel bonding, multiple Ether-
net interfaces are configured to behave as one, reducing the risk of a single-point-of-failure
in the typical switched Ethernet connection among cluster nodes and other cluster hard-
ware.
5. Configuration Considerations
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