a storage area network system has host computers , front - end san controllers connected via a bus or network interconnect to back - end san controllers , and physical disk drives connected via network interconnect to the be_sans to provide distributed high performance centrally managed storage . described are hardware and software architectural solutions designed to eliminate i / o traffic bottlenecks , improve scalability , and reduce the overall cost of san systems . in an embodiment , the be_san has firmware to recognize when , in order to support a multidisc volume , such as a raid volume , it is configured to support , it requires access to a physical disk attached to a second be_san ; when such a reference is recognized it passes assess commands to the second be_san . further , the be_san has firmware to make use of the physical disk attached to the second be_san as a hot - spare for raid operations .