Patent ID: 7603485

Claim:
A storage system comprising a first storage subsystem located at a main site and a second storage subsystem located at a remote site in relation to said first storage subsystem, and remotely copying data between said first storage subsystem and said second storage subsystem, wherein each of the storage subsystems controls transmitting data between a host computer and a storage apparatus the provides a plurality of logical units thereon, said logical units are configured from a storage extent for reading from and writing to said host computer, wherein said each storage subsystem includes: a plurality of controllers each having a local memory for retaining a command sent from said host computer, and a processor for controlling the data to and from a corresponding one of the logical units based on said command retained in said local memory; and a first inter-controller connection path connecting between a self-subsystem controller and an other-subsystem controller, wherein said local memory stores association information of a correspondence among said logical units and said controllers, and address information of said local memory in each of said controllers of the first subsystem and the second subsystem, wherein, upon receiving a command sent from said host computer for a target logical unit, a self-subsystem controller determines whether the target logical unit is associated with a self-subsystem controller or an other-subsystem controller based on said association information, and when the target logical unit is associated with said other-subsystem controller, said self-subsystem controller transfers said command to said other-subsystem controller based on said address information and stores said command therein, wherein a storage extent for retaining a command of each of said local memories of the self-subsystem controller and the other-subsystem controller is configured with a queue structure, said queue structure includes a receive queue for retaining a command received from said host computer, and a command queue for retaining a command for said processor to access the target logical unit designated in said command, and wherein, when the first inter-controller connection path connecting between said self-subsystem controller and said other-subsystem controller is blocked, said processor of said self-subsystem controller of said first storage subsystem stores a boot command for said another self-subsystem controller of said first storage subsystem in the queue of said local memory of said self-subsystem controller and copies the boot command for said another self-subsystem controller into a queue of said local memory of said another self-subsystem controller, and then said another self-subsystem controller sends a command for accessing data to said another other-subsystem controller of said second storage subsystem via a second inter-controller connection path connecting between another self-subsystem controller and another other-subsystem controller.