The present invention relates to a storage unit comprising: a channel control portion for receiving a data input/output request; a cache memory for storing data; a disk control portion for performing input/output processing on data in accordance with the data input/output request; and a plurality of disk drives for storing data, wherein at least two of the disk drives input data to and output it from the disk control portion at different communication speeds. Further, the storage unit has a plurality of communication paths provided to connect at least one of the disk drives in such a manner as to constitute a loop defined by the FC-AL fiber channel standards, so that the communication speeds can be set differently for these different communication paths.