Appendix E. Supplementary Software Information

The information in the following sections can assist in the management of the cluster software configuration.

E.1. Cluster Communication Mechanisms

A cluster uses several intra-cluster communication mechanisms to ensure data integrity and correct cluster behavior when a failure occurs. The cluster uses these mechanisms to:

The cluster communication mechanisms are as follows:

If a member determines that a time-stamp from another member is not up-to-date, it checks the heartbeat status. If heartbeats to the member are still operating, the cluster software takes no action. If a member does not update its time-stamp after some period of time, and does not respond to heartbeat pings, it is considered down.

The cluster remains operational as long as one cluster system can write to the shared partitions, even if all other communication mechanisms fail.

Note that shared partition is only used as a back-up in some two-member configurations. The network membership algorithm is the primary determining factor as to which cluster members are active and which are not. A member that is not updating its time-stamp in this configuration never causes a failover unless clumembd reports that the member is down.