Disk drive array with request fragmentation

A method of operating one or more disk drives through a programmable disk drive controller which is interfaced through a bus to a host computer, comprising the steps of:

• (a) occasionally issuing access requests from said host computer to said disk drive controller;
• (b) maintaining a queue, in said disk drive controller, for said access requests;
• (c) analyzing any newly received access requests, in said disk drive controller, to ascertain whether said access request is atomic;
• and, if said access request is not atomic, then fragmenting said access request into smaller access requests, until no resulting access request is not atomic;
• (d) enqueuing atomic access requests into said queue, together with execution-control markers which indicate groups of atomic operations which must be executed in strict sequence;
• (e) executing atomic access requests from said queue in an order which, except as constrained by said execution-control markers, is dynamically optimized in accordance with the instantaneous rotational phase of said disk drives;
• (f) when said controller detects an error condition during execution of an access request, then inserting one or more error handling requests into said queue, and servicing said error handling requests before servicing any further access requests;
• (g) returning said redesignated access request to its original designation.

A method of redundant memory access request execution, comprising the steps of:

• (a) providing a queue for access requests to a memory;
• (b) redesignating an access request when said access request detects a defect in said memory;
• (c) inserting error handling requests in said queue prior to said redesignated access request;
• (d) executing said error handling requests;
• and
• (e) returning said redesignated access request to its original designation.

A disk drive controller, comprising, on a common circuit board:

• a microprocessor;
• random-access memory which is read/write accessible by said microprocessor;
• a bus interface circuit, connected to said microprocessor and to a system bus connector;
• multiple connections for cabling to multiple separate disk drives;
• wherein said microprocessor comprises:
• means for maintaining a queue, in said disk drive controller, for access requests received;
• means for analyzing any newly received access requests, in said disk drive controller, to ascertain whether said access request is atomic;
• and, if said access request is not atomic, then fragmenting said access request into smaller access requests, until no resulting access request is not atomic;
• means for enqueuing atomic access requests into said queue, together with execution-control markers which indicate groups of atomic operations which must be executed in strict sequence;
• means for executing atomic access requests from said queue in an order which, except as constrained by said execution-control markers, is dynamically optimized in accordance with the instantaneous rotational phase of said disk drives.