Abstract: For a highly available replication system, a process is presented whereby, after a successful failover from primary to replica, with the replica now being the new primary, and where, at a later time, the original primary is subsequently restored to operation, a subset close to the minimal possible subset of data that needs to be transferred between the new and original primaries can be computed.

Abstract: A distributed locking system and method for a clustered system having a distributed system for storing cluster configuration information is provided. One aspect of the present invention allows a process or thread in a high availability solution to obtain a distributed lock on all relevant nodes in a clustered system. Another aspect of the present invention allows more than one thread to obtain a lock and perform a critical operation on different nodes concurrently.

Abstract: For use with a computer cluster having virtual memory logical devices associated therewith, a system and method for determining which of the virtual memory logical devices are shared devices and a computer cluster employing such system or method. The system includes: (1) a polling circuit that retrieves volume information from at least some of the virtual memory logical devices and (2) a matching circuit that determines which ones of the at least some of the virtual memory logical devices are shared devices as a function of the volume information.

Abstract: A method and apparatus are disclosed which perform a simple check of the network adapter by sending a message to an address of a local adapter. If the message is not sent, then a more in depth check of the network is performed. The local computer sends a request to a first remote computer to ping the adapter on the local computer. If this ping is successful, then the local computer sends a request to a second remote computer to ping the adapter on the local computer. The pinging by two computers provides confirmation that the network adapter is functional. If both of the pings are unsuccessful, then the address of the network adapter is moved to another adapter on another computer.

Abstract: A system and method of providing a quorum service which each system of a cluster registers with prior to a potential failover to insure proper functionality of the cluster is provided.