Patent ID: 7817626

Claim:
A storage subsystem connected to a host computer for receiving a write or read access from said host computer, comprising: a plurality of storage modules each connected to a storage device, and each having a controller for controlling the transfer of a packet based on said write or read access from said host computer to a target storage device connected to one of said plurality of storage modules; a switch connected to at least one of other storage modules; and a memory storing a transfer rule of said packet; wherein the transfer rule includes a first transfer rule related to a transfer direction and a second transfer rule related to a limitation of a number of paths, wherein said controller restricts the transfer direction of a command packet flowing through a path between two switches of said storage modules to a specific direction based on said first transfer rule, wherein a plurality of paths are configured between a first switch of a first storage module of said plurality of modules and a second switch of a second storage module of said plurality of modules; wherein said controller transfers said command packet headed from the first storage module to the second storage module via one of said plurality of paths, and transfers said command packet headed from the second storage module to the first storage module via a path that is different from said one path, and wherein said controller restricts, based on said second transfer rule, the number of paths, which cascade connect said plurality of storage modules, for at least one packet among a plurality of packets to be transferred among said plurality of storage modules so that said packet is not able to cross more than a certain number of paths at one time.