Method for host-based i/o workload balancing on redundant array

Abstract

A RAID storage system which attempts to balance the I/O workload between multiple redundant array controllers is presented. The RAID storage system of the invention utilizes a plurality of redundant array controllers which require static ownership of storage devices for WRITE access requests to the same redundancy parity group. Accordingly, a plurality of storage devices are provided in the system, each of which is owned by one of the redundant array controllers. Each storage device is coupled to both its owner controller and at least one other array controller. Each array controller coupled to a storage device has the ability to read and write data from and to the storage device. Each array controller has a processing queue from which pending read and write access requests are removed and then processed one at a time by the controller. A host computer is provided for dispatching read and write access requests to the redundant array controllers. WRITE access requests are dispatched only to the owner controller of the storage device to be written to. READ access requests may be dispatched to any one of the array controllers coupled to the storage device from which data is to be read. Load balancing among the array controllers is generally achieved by dispatching READ access requests to one controller or another in an attempt to offset WRITE access requests which must be dispatched to its owner controller.