Patent ID: 7562257

Claim:
A data storage system comprising: a plurality of disk storage devices for storing data; and at least a pair of controllers being connected to the plurality of disk storage devices via each different transmission paths, and performing access control of each disk storage device according to an access instruction from an upper level unit, wherein when one controller accesses the disk storage device via one transmission path and detects an error from a response result received from the disk storage device, one controller starts diagnosis processing, and requests the other controller to access, via the other transmission path, the disk storage device having been accessed, said other controller accesses, via the other transmission path, the disk storage device according to said request, and receives a response result from the disk storage device, said one controller receives said response result of the disk storage device from the other controller, and identifies whether a suspected fault location lies in the disk storage device or the transmission path from the response result, and wherein said one controller identifies that said suspected fault location lies in the disk storage device when detecting said error from the response result, and identifies that said suspected fault location lies in the transmission path when not detecting said error from the response result.