Disk drive recovering multiple codewords in data sectors using progressively higher order parity codewords

A disk drive comprising:

• a disk comprising a plurality of tracks, wherein each track comprises a plurality of data sectors including a parity sector, the parity sector comprising at least a P0 parity codeword, a P1 parity codeword, and a P2 parity codeword;
• a head actuated over the disk;
• and
• control circuitry operable to:
• read a plurality of the data sectors to generate a plurality of data codewords CW0-CWn;
• read the parity sector;
• decode the data sectors using an error correction code (ECC) decoder;
• when a single data codeword in the CW0-CWn is unrecoverable using the ECC decoder, recover the single data codeword using the P0 parity codeword;
• when two data codewords in the CW0-CWn are unrecoverable using the ECC decoder, recover the two data codewords using the P0 and P1 parity codewords;
• and
• when three data codewords in the CW0-CWn are unrecoverable using the ECC decoder, recover the three data codewords using the P0, P1 and P2 parity codewords;
• wherein:
• the P0 parity codeword is generated according to:
• P0=CW0⊕CW1⊕ . . . CWn;
• the P1 parity codeword is generated according to:
• P1=α0{circle around (x)}CW0⊕α1{circle around (x)}CW1⊕ . . . αn{circle around (x)}CWn;
• and
• the P2 parity codeword is generated according to:
• P2=α2·0{circle around (x)}CW0⊕α2·1{circle around (x)}CW1⊕ . . . α2·n{circle around (x)}CWn.

A method of operating a disk drive, the disk drive comprising

• a disk and a head actuated over the disk, wherein:
• the disk comprises a plurality of tracks;
• each track comprises a plurality of data sectors including a parity sector;
• and
• the parity sector comprising at least a P0 parity codeword and a P1 parity codeword;
• the method comprising:
• reading a plurality of the data sectors to generate a plurality of data codewords CW0-CWn;
• reading the parity sector;
• decoding the data sectors using an error correction code (ECC) decoder;
• when a single data codeword in the CW0-CWn is unrecoverable using the ECC decoder, recovering the single data codeword using the P0 parity codeword;
• and
• when two data codewords in the CW0-CWn are unrecoverable using the ECC decoder, recovering the two data codewords using the P0 and P1 parity codewords;
• wherein:
• the P0 parity codeword is generated according to:
• P0=CW0⊕CW1⊕ . . . CWn;
• and
• the P1 parity codeword is generated according to:
• P1=α0{circle around (x)}CW0⊕α1{circle around (x)}CW10 . . . αn{circle around (x)}CWn.

A method of operating a disk drive, the disk drive comprising

• a disk and a head actuated over the disk, wherein:
• the disk comprises a plurality of tracks;
• each track comprises a plurality of data sectors including a parity sector;
• and
• the parity sector comprising at least a P0 parity codeword, a P1 parity codeword, and a P2 parity codeword;
• the method comprising:
• reading a plurality of the data sectors to generate a plurality of data codewords CW0-CWn;
• reading the parity sector;
• decoding the data sectors using an error correction code (ECC) decoder;
• and
• decoder, recovering the unrecoverable data codewords using the parity
• when a single data codeword in the CW0-CWn is unrecoverable using the ECC decoder, recovering the single data codeword using the P0 parity codeword;
• when two data codewords in the CW0-CWn are unrecoverable using the ECC decoder, recovering the two data codewords using the P0 and P1 parity codewords;
• and
• when three data codewords in the CW0-CWn are unrecoverable using the ECC decoder, recovering the three data codewords using the P0, P1 and P2 parity codewords;
• wherein:
• the P0 parity codeword is generated according to:
• P0=CW0⊕CW1⊕ . . . CWn;
• the P1 parity codeword is generated according to:
• P1=α0{circle around (x)}CW0⊕α1⊕CW1⊕ . . . αn{circle around (x)}CWn;
• and
• the P2 parity codeword is generated according to:
• P2=α0{circle around (x)}CW0⊕α2·1{circle around (x)}CW1⊕ . . . α2·n{circle around (x)}CWn.