Disk array system for processing and tracking the completion of I/O requests

A disk array controller card configured to connect a host computer to an array of disk drives, the controller card comprising:

• a completion monitoring circuit, the completion monitoring circuit configured to apply a logic function to a variable-length sequence of completion values to monitor the completion status of an input/output (I/O) request being processed by the controller card, the I/O request generated by the host computer and specifying a transfer of data between the host computer and a plurality of the disk drives of the array;
• a plurality of controllers, each controller connected to and configured to control the operation of at least one respective disk drive of the array;
• and
• a microcontroller that runs a control program, the microcontroller configured via the control program to receive an I/O request from the host computer and to generate a plurality of completion values, the plurality of completion values generated such that application of the logic function to the plurality completion values produces a final completion value that is known to the completion monitoring circuit, the microcontroller further configured to transfer each completion value to a different respective controller that is invoked by the I/O request;
• wherein each invoked controller passes a respective completion value to the completion monitoring circuit upon finishing processing the I/O request, and wherein the completion monitoring circuit applies the logic function to the completion values received from the controllers and compares a result of the logic function to the final completion value to determine whether the last completion value of the plurality of completion values has been received.

In a disk array system which comprises an array of disk drives which are controlled by an array of controllers, a method of processing an input/output (I/O) request so as to efficiently detect the completion of processing of the I/O request, the I/O request generated by a host computer and specifying a transfer of data between the host computer and a variable number of disk drives, the method comprising the steps of:

• (a) providing a completion monitoring circuit, the completion monitoring circuit configured to apply a logic function to a variable-length sequence of completion values to monitor the completion status pending I/O requests;
• (b) in response to receipt of the I/O request from the host computer, generating a plurality of completion values and transmitting each completion value to a different respective controller that is invoked by the I/O request, the completion values generated such that application of the logic fuction to the plurality completion values produces a preselected final completion value that is known to the completion monitoring circuit;
• (c) at each controller invoked by the I/O request, when processing of the I/O request is complete, transferring the completion value transmitted to the controller in step (b) to the completion monitoring circuit;
• and
• (d) at the completion monitoring circuit, applying the logic function to the completion values transferred in step (c), and comparing an output of the logic function to the final completion value to detect the receipt of the last completion value.