Fibre channel input/output data routing system and method

Method for input/output (I/O) between host computer and control-unit 118, comprising: generating and storing in local memory 132 address control words specifying host memory 106 locations for data transfer and data check word generation and save field; responsive to data transfer requests including data to be stored in host memory and data check word, storing data-check-word in save field, and checking data corruption; responsive to data-transfer requests for data to be retrieved from host memory, generating data-check-words based on generation field and appending data-check-words to data. Data-check-words include: longitudinal (LRC)/ cyclical (CRC) redundancy check-word and checksum. I/O can be transport mode. I/O start rates are increased and response time reduced by providing data router 160 in channel of a channel subsystem allowing host bus adaptor (HBA) 154 to directly access host memory without storing I/O data in channel. Isolation for error checking and addressing of multiple address spaces is provided.