Two or more different elapsed time values are determined between transitions of a data signal applied to a magnetic write transducer of a heat-assisted magnetic recording apparatus. Two or more different power values of the laser are respectively associated with the two or more different elapsed time values. The two or more different power levels are selected to reduce differences between track widths of recorded marks having the two or more different elapsed time values.

According to one embodiment, a magnetic disk device includes a magnetic disk, a storage unit, a magnetic head, an error correction unit that, in a case where an error is detected in user data read by the magnetic head, performs error correction on a sector in which the error is detected in track units and acquires error correction data, and a control unit. The control unit controls reading/writing of user data, management data for managing a sector on which the error correction is performed in the track units, and the error correction data, and in a case where there is no host access, rewrites data on the track including the sector on which the error correction is performed, based on the user data stored in the track and the error correction data of the sector, in which the error is detected, of the track.

A storage array includes a plurality of hard disks, each of the hard disks is divided into a plurality of chunks, and a plurality of chunks of different hard disks form a chunk group by using a redundancy algorithm. The storage array obtains fault information of a faulty area in a first hard disk, and determines a faulty chunk storing the lost data according to the fault information. The storage array recovers the data in the faulty chunk by using another chunk in a chunk group to which the faulty chunk belongs and stores the recovered data in a recovered chunk. The recovered chunk is located in a second hard disk which is not a hard disk for forming the chunk group.

According to one embodiment, a disk device includes a disk, a head including a write head which writes data to the disk, a first read head which reads data from the disk, and is configured to detect a first value indicating a signal quality of read data during read processing, and a second read head which reads data from the disk, and is configured to detect a second value indicating a signal quality of read data during read processing, and a controller which determines whether there is a possibility that data cannot be read by the first read head and the second read head based on the first value and the second value.

A system includes a read/write module and a caching module. The read/write module is configured to access a first portion of a recording surface of a rotating storage device. Data is stored on the first portion of the recording surface of the rotating storage device at a first density. The caching module is configured to cache data on a second portion of the recording surface of the rotating storage device at a second density. The second portion of the recording surface of the rotating storage device is separate from the first portion of the recording surface of the rotating storage device. The second density is less than the first density.

An optical storage system includes an optical head configured to split a light beam into a higher power main beam and at least one lower power side beam. The optical storage system also includes a controller configured to alter an optical medium, via modulation of the higher power main beam according to a writing strategy waveform that defines at least n pulses for every n bits of data to be written to the medium, while processing a first signal resulting from the at least one lower power side beam being reflected from the medium and a second signal indicative of the writing strategy waveform to remove noise from the first signal caused by the higher power main beam to generate output indicative of the data directly after writing.

According to an embodiment, a track includes first sectors and a second sector. When write of a second data segment to a third sector that is one of the first sectors is requested from a host, a controller acquires the second data segment from the host and stores the second data segment in the memory, and reads a data set including all first data segments and all first information pieces from the track and stores the data set in the memory. The controller acquires a second information piece of the third sector, and updates a first data segment and a first information piece read from the third sector in the data set in the memory with the second data segment and the second information piece. The controller calculates a second parity while the updated data set to the track, and writes the second parity to the second sector.

According to an embodiment, a track includes first sectors and a second sector. When write of a second data segment to a third sector that is one of the first sectors is requested from a host, a controller acquires the second data segment from the host and stores the second data segment in the memory, and reads a data set including all first data segments and all first information pieces from the track and stores the data set in the memory. The controller acquires a second information piece of the third sector, and updates a first data segment and a first information piece read from the third sector in the data set in the memory with the second data segment and the second information piece. The controller calculates a second parity while the updated data set to the track, and writes the second parity to the second sector.

A magnetic disk device includes a plurality of tracks and a controller. The controller receives write data to be written to a first sector of a track, generates a first data string based on the write data and a logical identifier for the first sector, attempts to cause the first data string to be written to the first sector, determines whether a write error has occurred while the first data string is written to the first sector, generates a second data string based at least in part on the first data string, and in response to determining that no write error has occurred while the first data string is written to the first sector, writes a parity data string that is based at least in part on the second data string to a second sector of the track that stores parity data for the track.

A tape drive allows for an increased track density by partially overlapping adjacent tracks as each successive track is written. Each successive track overwrites a portion of the width of the previous track, thereby reducing the width of the previous track. This process can be applied repeatedly thereby producing an arrangement of shingled data tracks across the width of the tape. In an embodiment, single-pass verification of data written in this manner is accomplished using a head assembly with two read heads per track. A first read head positioned behind the write head verifies that the data written is correct, and a second read head positioned over the previous track verifies that data on the previous track remains intact after being partially overwritten.