# US 2022/0044702 A1 · Magnetic disk device and error correction method > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2022/0044702 A1 - Document ID: US20220044702A1 - Status: Published application - Kind: A1 - Application number: 17/170,052 - Filed: 2021-02-08 - Published: 2022-02-10 - Earliest claimed: 2020-08-05 - Assignees: Kabushiki Kaisha Toshiba; Toshiba Electronic Devices & Storage Corporation - Applicants: Kabushiki Kaisha Toshiba; Toshiba Electronic Devices & Storage Corporation - Inventors: Nobuhiro Maeto - Web page: https://patentgrep.com/patent/US20220044702A1 ## CPC - G11B 20/1889: {with discs} - G11B 20/1816: {Testing} - G11B 20/1833: {by adding special lists or symbols to the coded information (G11B20/1806, G11B20/1866 take precedence)} - G11B 2020/183: {wherein at least one additional attempt is made to read or write the data when a first attempt is unsuccessful} - G11B 2020/185: {using an low density parity check [LDPC] code} - G11B 2220/2516: Hard disks - G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R) ## Abstract According to one embodiment, a magnetic disk device includes a disk, a head that writes data to the disk and reads data from the disk, and a controller that executes error correction on a first sector which is unreadable in a first track from an initial reading time of initially one-round reading the first track of the disk based on first parity data corresponding to the first track. ## Claims ### Claim 1 A magnetic disk device comprising: a disk; a head that writes data to the disk and reads data from the disk; and a controller that executes error correction on a first sector which is unreadable in a first track from an initial reading time of initially one-round reading the first track of the disk based on first parity data corresponding to the first track. ### Claim 2 (depends on 1) The magnetic disk device according to claim 1, wherein in a case where the first sector becomes readable by executing the error correction, the controller re-assigns the first sector based on quality of the first sector. ### Claim 3 (depends on 2) The magnetic disk device according to claim 2, wherein the controller starts reading the first track from a first position of the first track in a circumferential direction, and in a case where the first sector is unreadable at a second position of the first track in the circumferential direction, the controller one-round reads the first track and executes the error correction on the first sector. ### Claim 4 (depends on 3) The magnetic disk device according to claim 3, wherein, in a case where the first sector becomes readable when the error correction is executed between the initial reading time of one-round reading the first track with starting reading from the first position and a third reading time of three-round reading the first track with starting reading from the first position, the controller re-assigns the first sector based on the quality of the first sector. ### Claim 5 (depends on 3) The magnetic disk device according to claim 3, wherein the controller checks the quality of the first sector based on the number of all bits in first data of the first sector corrected by the error correction. ### Claim 6 (depends on 3) The magnetic disk device according to claim 3, wherein the controller checks the quality of the first sector based on the number of Parity Checks which are unsatisfied when LDPC is executed on first data of the first sector. ### Claim 7 (depends on 3) The magnetic disk device according to claim 3, wherein the controller checks the quality of the first sector based on a metric difference between a selection path and a competition path in Viterbi decoding processing for first data of the first sector. ### Claim 8 (depends on 3) The magnetic disk device according to claim 3, wherein the controller checks the quality of the first sector based on a drop in a waveform of first data of the first sector. ### Claim 9 (depends on 2) The magnetic disk device according to claim 2, wherein, in a case where the first sector is re-assigned to a second sector of a second track different from the first track, the controller generates the first parity data based on all sectors of the first track other than the first sector and the second sector. ### Claim 10 (depends on 9) The magnetic disk device according to claim 9, wherein the controller reads all the sectors of the first track other than the first sector, reads the second sector of the second track, and generates the first parity data based on all the sectors of the first track other than the first sector and the second sector. ### Claim 11 (depends on 2) The magnetic disk device according to claim 2, wherein, in a case where the first sector is re-assigned to a second sector of a second track different from the first track, and it is determined that the first sector is not used, the controller generates the first parity data based on all sectors of the first track other than the first sector. ### Claim 12 (depends on 11) The magnetic disk device according to claim 11, wherein the controller reads all the sectors of the first track other than the first sector, and generates the first parity data based on all the sectors of the first track other than the first sector. ### Claim 13 (depends on 2) The magnetic disk device according to claim 2, wherein, in a case where a third sector different from the first sector which is unreadable in the first track is error-corrected based on the first parity data, and the error-corrected third sector is readable, the third sector is re-assigned based on quality of the third sector. ### Claim 14 A magnetic disk device comprising: a disk in which data is written in 4 k sector format or higher; a head that writes data to the disk and reads data from the disk; and a controller that executes error correction on a first sector of 4 k or more which is unreadable in a first track from an initial reading time of initially one-round reading the first track of the disk based on first parity data corresponding to the first track. ### Claim 15 An error correction method which is a re-assigning method for a magnetic disk device including a disk and a head that writes data to the disk and reads data from the disk, the method comprising: executing error correction on a first sector which is unreadable in a first track from an initial reading time of initially one-round reading the first track of the disk based on first parity data corresponding to the first track. ### Claim 16 (depends on 15) The error correction method according to claim 15, further comprising: re-assigning the first sector based on quality of the first sector in a case where the first sector becomes readable by executing the error correction. ### Claim 17 (depends on 16) The error correction method according to claim 16, further comprising: starting reading the first track from a first position of the first track in a circumferential direction; and one-round reading the first track and executing the error correction on the first sector in a case where the first sector is unreadable at a second position of the first track in the circumferential direction. ### Claim 18 (depends on 17) The error correction method according to claim 17, further comprising: re-assigning the first sector based on the quality of the first sector in a case where the first sector becomes readable when the error correction is executed between the initial reading time of one-round reading the first track with starting reading from the first position and a third reading time of three-round reading the first track with starting reading from the first position. ### Claim 19 (depends on 17) The error correction method according to claim 17, further comprising: checking the quality of the first sector based on the number of all bits in first data of the first sector corrected by the error correction. ### Claim 20 (depends on 17) The error correction method according to claim 17, further comprising: checking the quality of the first sector based on the number of Parity Checks which are unsatisfied when LDPC is executed on first data of the first sector.