Communication system for an array of direct access storage devices (DASD) that provides for bypassing one or multiple DASD

摘要

A communication system for an array of DASD includes a plurality of loop resiliency circuits and a plurality of selection circuits. The DASD array includes a plurality of DASD slots. Each DASD slot may receive a DASD, and each DASD receives power from a regulator. The loop resiliency circuits form at least a first communication path. Each loop resiliency circuit is associated with one of the DASD slots and selectively includes the associated DASD slot in the first communication path based on a selection signal. The plurality of selection circuits are also associated with one of the DASD slots; and therefore, are also associated with one of the plurality of loop resiliency circuits. Each selection circuit is connected to the associated DASD slot and receives output from the regulator in the associated DASD slot. Based on the regulator output, or a lack thereof, the selection circuit generates a selection signal for the associated loop resiliency circuit. Besides being serially connected to form a single communication path, the loop resiliency circuits can be divided into groups wherein the loop resiliency circuits in each group are serially connected to form a communication path. Separate loop resiliency circuits then selectively connect these communication paths to a main communication path including an initiator. As a further alternative, a second initiator can be selectively placed in one of the communication paths via another loop resiliency circuit.