Disk array apparatus that only calculates new parity after a predetermined number of write requests

A disk array apparatus for use with a host computer, said disk array apparatus comprising:

• a disk array having a plurality of disk apparatuses for storing data, including old data and one disk apparatus for storing parity information, including old parity information;
• dummy data stored in empty areas of said plurality of disk apparatuses for storing data;
• dummy parity information stored in empty areas of said disk apparatus for storing parity information;
• access processing means for forming new parity information on the basis of new data, old data and old parity information, and updating said old data and said old parity information of said disk array when said new data is received, said access processing means being adapted to count the number of times the data has been updated and update said disk array with said new parity information and said new data after a pre-specified number of data updates, further, in the case of deletion of the data, said access processing means being adapted to update said old data with said dummy data and said old parity information with said dummy parity information;
• non-volatile cache memory means for storing at least one of said old data and said old parity information, said non-volatile cache memory means further storing processing stage data indicative of a processing stage of said access processing means;
• and
• cache control means for holding said old parity information in said cache memory means without allowing the new parity information to be formed by said access processing means until said access processing means has received new data in response to a write request from an upper apparatus a predetermined number of times, and searching said cache memory means for at least one of said old data and said old parity information and supplying at least one of said old data and said old parity information to said access processing means for forming said new parity information.

A disk array apparatus for use with a host computer, said disk array apparatus comprising:

• a disk array having a plurality of disk apparatuses for storing data, including old data, and one disk apparatus for storing parity information, including old parity information;
• access processing means for forming new parity information on the basis of new data, old data and corresponding old parity information, said access processing means updating said old data and said old parity information of said disk array with said new parity information and said new data in response to a pre-specified number of data updates, said access processing means being adapted to count the number of times data has been updated;
• cache memory means partitioned into an updating data area and at least one of a data memory area and a parity memory area, said cache memory means for storing at least one of said old data and said old parity information, whereby only said new data is stored in said updating data area, only said old parity information is stored in said parity memory area and only said old data is stored in said data memory area;
• and
• cache control means for holding said old parity information in said cache memory means without allowing the new parity information to be formed by said access processing means until said access processing means has received new data in response to a write request from an upper apparatus a predetermined number of times, and searching said cache memory means for at least one of said old data and said old parity information and, if found, supplying at least one of said old data and said old parity information to said access processing means for forming said new parity information.

An array controller for controlling a disk array having a plurality of disk apparatuses for storing data and one disk apparatus for storing parity information in response to a input/output request from an upper apparatus, comprising:

• access processing means for forming a new parity information on the basis of new data, old data, and an old parity information, said access processing means being adapted to count the number of times the data has been updated, said access processing means further updating said old data and said old parity information of said disk array with said new parity information and said new data in response to a pre-specified number of data updates;
• cache memory means for storing at least one of said old data and said old parity information stored in said disk array;
• and
• cache control means for holding said old parity information in said cache memory means without allowing the new parity information to be formed by said access processing means until said access processing means has received new data in response to a write request from an upper apparatus a predetermined number of times, and searching at least one of said old data and said old parity information stored in said cache memory means, said cache control means further supplying at least one of said old data and said old parity information to said access processing means.