Patent ID: 8578073

Claim:
A storage system, comprising: a first storage subsystem having a first logical volume to be accessed by a host computer; and a second storage subsystem connected to the first storage subsystem and having a second logical volume to be mapped to the first logical volume; wherein the first storage subsystem includes: a memory having definition information for defining a plurality of logical paths between the first logical volume and the second logical volume through which I/O from the host computer to the first logical volume is transferred, and a transfer mode of the I/O through the plurality of logical paths; and a controller for controlling the transfer of the I/O based on the definition information, wherein if the transfer mode is changed to a single path mode in which the I/O is transferred using one of the plurality of logical paths, the controller registers the single path mode as the transfer mode in the definition information, wherein if the transfer mode is changed to a multi path mode in which the I/O is transferred using the plurality of logical paths for balancing I/O load, the controller checks whether the second storage subsystem supports the multi path mode and registers the multi path mode as the transfer mode in the definition information in the case that the second storage subsystem supports the multi path mode or notifies that the plurality of logical paths is not switched to the multi path mode in the case that the second storage subsystem does not support the multi path mode, wherein the controller detects an I/O pattern of the I/O if the controller receives the I/O, wherein if the detected I/O pattern of the I/O is a sequential access, the controller switches the transfer mode, from the multi path mode to the single path mode, and wherein if the detected I/O pattern of the I/O is a random access, the controller checks whether the second storage subsystem supports the multi path mode or not, switches the transfer mode from the single path mode to the multi path mode in the case that the second storage subsystem supports the multi path mode.