Abstract: The invention provides a method and apparatus for generating a signature signal which indicates a probable location for an error-causing mechanism within a digital system, where the digital system has control-signal and data-signal carrying busses and error detection means for detecting error conditions in the signals carried by those busses. The signature generating method comprises the steps of: counting the total number of errors detected by the error detection means during a signature generating run; and counting the number of errors detected by the error detection means during a signature generating run where those errors were accompanied by the presence of accompanying signals on the signal-carrying busses, the accompanying signals being ones which belong to a predefined subset of all signals appearing on the system signal-carrying busses.

Abstract: The data storage subsystem of the present invention uses a large plurality of small form factor disk drives to implement an inexpensive, high performance, high reliability disk drive memory that emulates the format and capability of large form factor disk drives. The data transmitted by the associated computer system is used to generate redundancy information which is written with the data across N+M disk drives in a redundancy group in the data storage subsystem. To clear the redundancy accumulator memory, an associated pointer memory is used to indicate the ones of the redundancy accumulator memory byte positions that were used in the previous redundancy calculation. As data is received from the computer system, the pointer memory is checked to determine whether this next byte position need be reset to erase the previously stored redundancy calculation residue. If not, the data is simply stored therein.