Abstract: A data storage system for transferring data between a host computer/server and a bank of disk drives through a system interface. The system interface includes: a plurality of first directors coupled to the host computer/server; a plurality of second directors coupled to the bank of disk drives; a cache memory; and a data transfer section coupled to the plurality of first directors, the second directors, and the cache memory. A messaging network is coupled to the plurality of first directors and the plurality of second directors. The first and second directors control data transfer between the host computer and the bank of disk drives in response to messages passing between the directors through the messaging network as such data passes through the memory via the data transfer section. A service processing network is provided for interfacing a plurality of service processing units to the plurality of first and second directors through a plurality of redundant communication channels.