Mass storage data integrity-assuring technique utilizing sequence and revision number metadata

A method of detecting and correcting errors arising from input/output I/O operations on user data stored in storage media of a mass information storage system, comprising the steps of:

• writing sequence number metadata with each of a plurality of associated groups of user data to identify a group-write I/O operation which wrote the groups of user data;
• writing revision number metadata with the user data to identify a partial-write I/O operation on each of less than all of the groups of user data while other remaining ones of the groups of user data are not written;
• writing parity metadata associated with each group of user data to describe each group of user data;
• writing separate sequence number metadata, revision number metadata and parity metadata on the storage media at a separate location from the groups of user data, the separate sequence number metadata and revision number metadata being substantial duplicates of the sequence number metadata and revision number metadata associated with each group of user data, the separate parity metadata describing the collective user data of all of the groups;
• correcting the user data of any group having an incorrect sequence number which is different from the sequence numbers of two other groups by using the separate parity metadata and user data from the groups having correct sequence numbers;
• and
• correcting the user data of any group having an incorrect revision number which occurred before the separate revision number metadata by using the separate parity metadata and the user data from all of the groups having correct revision numbers.

A redundant array of independent disks (RAID) mass information storage system, comprising an array controller and at least one redundancy group connected to the array controller, each redundancy group including a plurality of disk drives as storage media and a disk controller connected to the disk drives, the array controller and the disk controller each including a processor executing programmed instructions to detect and correct errors arising from input/output (I/O) operations on user data stored in a full stripe written on the plurality of disk drives of the redundancy group, the processors operatively:

• writing sequence number metadata to each of the plurality of disk drives with the user data to identify the stripe which contains the user data collectively written to the plurality of disk drives;
• writing revision number metadata to each of the plurality of disk drives with the user data to identify each read modify write I/O operation performed on the user data of a single disk drive after the stripe had been previously written;
• writing separate sequence number metadata, revision number metadata and parity metadata to a separate disk drive of the redundancy group as part of the stripe, the separate sequence number metadata and revision number metadata being substantial duplicates of the sequence number metadata and revision number metadata associated with the user data of the stripe contained on each other disk drive of the redundancy group, the separate parity metadata of the separate disk drive describing the all of the user data of the stripe contained on all of the other disk drives;
• correcting the user data of the stripe obtained from a disk drive when the user data of the stripe has a sequence number which is different from the sequence numbers of the user data of the stripe obtained from two other disk drives by using the separate parity metadata and user data of the stripe having correct sequence numbers in an error correcting algorithm;
• and
• correcting the user data of the stripe obtained from a disk drive when the user data of the stripe has an incorrect revision number which is different from the separate revision number metadata by using the parity metadata obtained from the separate disk drive and the user data from the disk drives of the stripe having correct revision numbers in an error correcting algorithm.