FailSafe provides a general facility for providing highly available services. It is supported on IRIX systems.
If a failure occurs, a different node in the cluster restarts the highly available services of the failed node. To clients, the services on the replacement node are indistinguishable from the original services before failure occurred. It appears as if the original node has crashed and rebooted quickly. The clients notice only a brief interruption in the highly available service.
In a FailSafe environment, nodes can serve as backup systems for other nodes. Unlike the backup resources in a fault-tolerant system, which serve purely as redundant hardware for backup in case of failure, the resources of each node in a highly available system can be used during normal operation to run other applications that are not necessarily highly available services. All highly available services are owned by one node in the cluster at a time.
Highly available services are monitored by the FailSafe software. If a failure is detected on any of these components, a failover process is initiated. Using FailSafe, you can define a failover policy to establish which node will take over the services under what conditions. This process consists of resetting the failed node (to ensure data consistency), performing recovery procedures required by the failed over services, and quickly restarting the services on the node that will take them over.
This paper discusses the following aspects of FailSafe operations: