Using multiple controllers together to create data spans

Abstract

A data storage system includes a pluralierty of controllers in a master/slave N-way controller topology. The master controller is coupled to a host system, and each controller is operatively coupled to one of a plurality of data unit arrays. The plurality of data unit arrays each include a plurality of disk units that are linked together. The linked disk units appear as a continuous logical unit and each data unit array forms a data span, such that the plurality of data unit arrays form N-way data spans. Each controller is adapted to transfer data between the data units and the master controller in response to instructions therefrom based on a data configuration. The data is then transferred between the master controller and the host system. The master controller is adapted to balance I/O requests amongst the plurality of controllers and re-direct an I/O request directed to a failed controller to an active controller. Alternatively, the data storage system includes a plurality of controllers in a peer-to-peer N-way controller topology. Any one active controller is adapted to transfer data between the data units and the host system in response to instructions therefrom and balance I/O requests amongst the plurality of controllers and re-direct an I/O request directed to a failed controller to an active controller. Advantages include automatic copying of the host data to an alternate controller for data protection. In addition, if the spans are setup as a RAID 0+5 or some other similar configuration, the workload is automatically distributed among the various controllers.