Abstract: Apparatus and methods are provided for efficiently implementing logical-device reservations in a cluster computer system. The apparatus includes cooperating controllers programmed in firmware around a distributed reservation table. The apparatus manages access to a logical device, with first and second nodes with respective bus controllers communicatively coupled to each other and to a logical device by means of a bus. The first controller receives a request to reserve the logical device and, in response, communicates a reservation request for the logical device over the bus to the second controller for execution by the second controller. In response to the communicated reservation request, the second controller reserves the logical device for the first node.

Abstract: Apparatus and methods for rebuilding logical I/O devices in a cluster computer system. The apparatus include controllers programmed to cooperate towards this end. The apparatus has first and second nodes with respective bus controllers communicatively coupled to each other and to the logical I/O device by means of a bus. The first controller receives a request to rebuild the logical I/O device and, in response, conditionally communicates a rebuild request for the logical I/O device over the bus to the second controller. (The logical I/O device can be a logical device depending from a multi-logical-device, third controller.) Before conditionally communicating, the apparatus determines whether a rebuild of a logical I/O device is already in progress and, when a rebuild is already in progress, aborts the new request to rebuild. When an rebuild is not already in progress, the apparatus then sets a state variable to indicate that a rebuild is now in progress.

Abstract: Methods for re-configuring a cluster computer system of multiple or more nodes when the cluster experiences communications failure. First and second nodes of the cluster have respective channel controllers. A SCSI channel and the controllers communicatively connect the multiple nodes. When a node becomes aware of a possible communications failure, the node attempts to determine the authenticity the failure and responds according to the determined authenticity. According to one method, a first node detects heartbeat node-to-node communications failure on the channel and then tests a physical drive on the channel. If the testing is successful, the node kills the other node. If the testing is unsuccessful, the first node commits suicide. In one embodiment, the coupling includes multiple channels communicatively coupling the first and second nodes and the first node selecting one of the channels for node-to-node communications.