Abstract: Data storage systems using a RAID-4 or RAID-5 organization divide an application I/O request into a number of individual I/O requests, each of which is contained within the boundaries of a single strip. The data blocks of each chunk on a strip responsive to an I/O request can form a complex geometric pattern requiring complicated operations to perform the I/O request. To simplify the necessary operations, each individual I/O request to a strip is divided into at most three requests targeted to data blocks forming a rectangle and each of these rectangles are processed as a unit. If a data block within a rectangle is unavailable, then the request to that rectangle is further subdivided into at most two requests targeted to data blocks forming smaller, non-overlapping rectangles which collectively are the original rectangle.

Abstract: A data storage system using a RAID array and a logging process and apparatus that identifies a parity block that may not contain the proper parity for its associated data blocks and which prevents such inconsistent parity information from being used in the regeneration of unavailable data. A small fraction of the blocks of each disk are dedicated to storing parity metadata bits. The parity metadata is associated with the parity blocks and identifies whether or not each parity block contains the proper parity information for its associated data blocks or may contain invalid information. The data integrity of the RAID array is preserved by preventing the generation of undetected corrupt data.