According to one embodiment, a magnetic disk device includes a disk including a first track including a first parity sector and a second track including a second parity sector, a head that writes data to the disk and reads data from the disk, and a controller that writes, to the first parity sector, a third parity sector obtained by XORing a first sector group included in each of the first track and the second track, and writes, to the second parity sector, a fourth parity sector obtained by XORing a second sector group different from the first sector group, included in each of the first track and the second track.

The present disclosure is directed to a data storage device that includes a refresh monitor based on a learning based feedback control. The refresh monitor is used to control refresh operations to account for effects of writes to media, e.g., adjacent track interference (ATI). Read operations are analyzed to derive damage information usable to update one or more probability distributions, upon which the learning is updated or reinforced and carried forward. In one embodiments, the data storage device includes control circuitry configured to maintain a refresh monitor based on a learning system, analyze a read operation with the refresh monitor; adjust the refresh monitor by updating the one or more probability distributions based on the analyzed read operation; and execute a refresh operation to refresh data based on the adjusted refresh monitor.

A magnetic disk device includes a disk including a plurality of error sectors including a defect, a first track having a first parity sector, and a controller. The controller is configured to, upon receiving a write command to write first data in a first region of a portion of the first track, which is a portion of the first track, first perform an XOR operation on all sectors of the first track other than one or more sectors of the first region and the first parity sector of the first track, and then write the first data in the one or more sectors of the first region, perform a second XOR operation on the one or more sectors of the first region and the result of the first XOR operation, and write the result of the second XOR operation in the first parity sector.

According to one embodiment, a magnetic disk device includes a disk including two first servo sectors and at least a second servo sector, a head, and a controller, wherein the first servo sector includes burst data and a first data pattern written before the circumferential direction of the burst data, the second servo sector includes the burst data, the first data pattern, and a second data pattern written after the circumferential direction of the burst data, a first frequency of the first data pattern is different from a second frequency of the second data pattern, and a first length of the first data pattern is different from a second length of the second data pattern.

According to one embodiment, a magnetic disk device includes a disk including two first servo sectors and at least a second servo sector, a head, and a controller, wherein the first servo sector includes burst data and a first data pattern written before the circumferential direction of the burst data, the second servo sector includes the burst data, the first data pattern, and a second data pattern written after the circumferential direction of the burst data, a first frequency of the first data pattern is different from a second frequency of the second data pattern, and a first length of the first data pattern is different from a second length of the second data pattern.

According to one embodiment, a magnetic disk device includes a disk including two first servo sectors and at least a second servo sector, a head, and a controller, wherein the first servo sector includes burst data and a first data pattern written before the circumferential direction of the burst data, the second servo sector includes the burst data, the first data pattern, and a second data pattern written after the circumferential direction of the burst data, a first frequency of the first data pattern is different from a second frequency of the second data pattern, and a first length of the first data pattern is different from a second length of the second data pattern.

A method for operating a storage controller to write to a group of multi-actuator disk drives includes receiving a data stream, performing RAID mapping to a preselected RAID level, organizing the data stream into at least one data stream, creating at least one parity data stream, organizing each data stream and parity data stream into blocks of data, dividing each data stream and each parity data stream into groups of blocks of data assigned to a logical unit representing a drive and an actuator, blocks of data from a data stream and parity stream assigned to a different drive, sequential groups of blocks of data assigned substantially equally to logical units representing actuators in each drive, providing each group of blocks of data to a target port associated with the drive to which it has been assigned, and sending each group of blocks of data from the target port.

A method for performing error recovery for data stored on a track of a storage device, in which the method includes: receiving a request to read the data from the storage device, identifying a plurality of sectors of the track to be read in response to the request, reading the data from the plurality of sectors of the track and parity data, based on the data read from the plurality of sectors, determining whether any of the plurality of sectors corresponds to a failed sector, and recovering a portion of the data from the failed sector using the parity data and portions of the data stored in remaining ones of the plurality of sectors.

According to one embodiment, a magnetic disk device includes a disk including a first track including a first sector, a second sector, and a first parity sector, a head, and a controller configured to, when writing a second track adjacent to the first track in the first direction, even if, in a third sector of the second track adjacent to the first sector in the first direction, a first upper limit in a second direction opposite to the first direction, continue the processing of writing data to the third sector, and if, in a fourth sector adjacent to the second sector in the first direction, a second upper limit in the second direction, stop the processing of writing data to the fourth sector.

Techniques perform data access to a disk array. The disk array includes a parity disk and a plurality of data disks. Via such techniques, data is written to the parity disk in the disk array in response to a write request to a failed data disk in the disk array when the disk array is in a degraded state; and corresponding degraded storage position information is set in disk resource mapping information so as to indicate that the data are stored in the parity disk. Accordingly, enormous computing resources can be saved, and I/O operations required by reads in the degraded state can be reduced.