Method and apparatus for ensuring system configuration data structure coherency across multiple controllers in a data storage system

A computer program product for ensuring system configuration data structure coherency across multiple controllers in a data storage system, the computer program product comprising a computer readable storage medium and a computer program mechanism embedded therein, the computer program mechanism comprising:

• a semaphore locking program module for synchronizing modifications by a first controller to its respective system configuration data structure, and for synchronizing modifications by other controllers to their respective system configuration data structures, the program module including instructions for:
• detecting, by a first controller, a change in the system configuration of the data storage system;
• reserving, by the first controller, a predetermined device, such that the predetermined device once reserved cannot be reserved by any other controller;
• modifying, by the first controller, its respective system configuration data structure to include the change;
• notifying, by the first controller, at least one other controller of the change;
• and,
• in response to the notifying, updating, by the at least one other controller, its respective system configuration data structure to include the change, the updates to each respective controller's system configuration data structure being synchronized such that each respective system configuration data structure accurately represents any change to the system configuration of the data storage system.

An disk array controller for ensuring system configuration data structure coherency across multiple controllers in a data storage system, the disk array controller comprising:

• a memory having a system configuration data structure, a reserve/release synchronization data structure, and a semaphore locking procedure stored therein, the system configuration data structure including structural, operating status, and relationship information for at least a subset of the components of the data storage system, the reserve/release data structure including identification of a predetermined device, the semaphore locking procedure using the information in the reserve/release command data structure to reserve the predetermined device before:
• (a) making any modifications to the system configuration data structure that reflect a change in the system configuration of the data storage system;
• and, (b) notifying any other components in the data storage system of the change;
• and,
• a processing unit coupled to the memory, for executing the semaphore locking procedure.

A computer system comprising:

• a host computer;
• a data storage subsystem including a plurality of data storage devices configured as an array and coupled with said host computer;
• a plurality of storage device array controllers for ensuring configuration data structure coherency across said plurality of controllers, each storage device controller including:
• a memory having a configuration data structure, a device reserve/release synchronization data structure, and a semaphore locking procedure stored therein;
• the system configuration data structure including information for at least a subset of the data storage storage devices;
• the reserve/release data structure including identification of a predetermined device, the semaphore locking procedure using the information in the reserve/release command data structure to reserve the predetermined device before:
• modifying the configuration data structure and, notifying any other device in the data storage system of the change;
• and, a processing unit coupled to the memory, for executing the semaphore locking procedure.