International Business Machines Corporation

Govindaraju Gnanasivam

Krishnakumar Rao Surugucchi

Mohan Babu Rowlands

Nallakumar Meiyappan

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.

Apparatus and method for implementing raid devices in a cluster computer system

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. The apparatus determines whether the first controller receiving the rebuild request is a master controller, and when it is not, communicates from the first, receiving controller to the master controller a rebuild request for the logical I/O device. The master controller directs the rebuilding of the logical I/O device, including determining within which controller the logical I/O device is reserved, and when the reserving controller is not the master controller, communicating from the master controller to the reserving controller a rebuild request for the logical I/O device. The reserving controller rebuilds the logical I/O device.

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Milpitas, CA, United States of America

Govindaraju Gnanasivam