A disk device includes a top cover and a disk medium with a recording surface. The top cover includes a center horizontal portion having a surface which extends from a center point of the disk medium along the recording surface to an outer peripheral portion, a curved portion having a surface which extends from the outer peripheral portion of the center horizontal portion in a direction away from the recording surface, and an outer horizontal portion having a surface which extends from the curved portion in a direction away from the center point and along the recording surface. The recording surface includes a first zone in which data is set to be written, and a second zone in which data is set not to be written, the second zone being disposed adjacent to the first zone on an outer edge side of the disk medium from the first zone.

In an optical disc apparatus that records and reproduces data onto and from an optical disc in units of predetermined block, an information divider divides the data so as to reduce an amount of the data included in each of blocks when a recording state of the optical disc does not satisfy a predetermined criterion, and reproduces recording data in units of the block by adding sub-information including a value indicating the amount of the data included in each of the blocks. An error-correction encoder circuit encodes the recording data in a first error-correction code format, and a recorder converts encoded recording data into a recording signal, and records the recording signal onto the optical disc. A quality evaluator circuit produces an evaluation value indicating a recording quality based on a result of reproducing the recording signal recorded on the optical disc.

A method for writing data onto a medium on which data are stored in tracks includes encoding the data into at least one codeword, and writing a respective portion of each of the at least one codeword onto respective different tracks on the medium. The writing may include writing a respective portion of each of the at least one codeword onto respective different adjacent tracks on the medium. Another method for reading data includes positioning a plurality of read heads to read codewords that have been written across multiple tracks of a medium. Each read head in the plurality of read heads reads a different portion of the first group of the multiple tracks, and where each different portion of the multiple tracks overlaps at least one other different portion of the multiple tracks. Signals are detected from the plurality of read beads, and the detected signals are decoded.

A method for writing data onto a medium on which data are stored in tracks includes encoding the data into at least one codeword, and writing a respective portion of each of the at least one codeword onto respective different tracks on the medium. The writing may include writing a respective portion of each of the at least one codeword onto respective different adjacent tracks on the medium. Another method for reading data includes positioning a plurality of read heads to read codewords that have been written across multiple tracks of a medium. Each read head in the plurality of read heads reads a different portion of the first group of the multiple tracks, and where each different portion of the multiple tracks overlaps at least one other different portion of the multiple tracks. Signals are detected from the plurality of read beads, and the detected signals are decoded.

A shingled magnetic recording (SMR) hard disk drive (HDD) is configured with a multi-level cache. To expedite execution of read commands, the SMR HDD is configured to generate and store a Bloom filter in a memory that can be quickly accessed by the drive controller whenever data are stored in certain levels of the multi-level cache. When data are flushed from one level of media cache to an SMR band included in a lower level of media cache, a Bloom filter is generated based on the logical block addresses (LBAs) stored in that SMR band. Thus, when the SMR HDD receives a read command for data that are associated with a particular LBA and are stored in an SMR region of the HDD, the drive controller can query the Bloom filter for each different SMR region of the HDD in which data for that LBA can possibly be stored.

According to one embodiment, a magnetic disk device including a disk, a head, and a controller which sets a first track pitch based on fringing when a second track is written, sets a second track pitch based on fringing when a third track is written, calculates a difference between the first track pitch and the second track pitch, sets, when the difference is less than or equal to a reference value, an area to which the first track is written in a first recording area, and sets, when the difference is greater than the reference value, the area to which the first track is written in a second recording area.

An exemplary write method disclosed herein includes receiving a request to write data to a consecutive sequence of logical block addresses (LBAs); identifying a first non-contiguous sequence of data tracks mapped to a first portion of the consecutive sequence of LBAs; and identifying a second non-contiguous sequence of data tracks mapped to a second portion of the consecutive sequence of LBAs, where the second portion sequentially follows the first portion. The method further includes writing the data of the second portion of the consecutive sequence of LBAs to the first non-contiguous sequence of data tracks during a first pass of a transducer head through the radial zone and writing the data of the first portion of the consecutive sequence of LBAs to the second non-contiguous sequence of data tracks during a second, subsequent pass of the transducer head through the radial zone.

A set of encoded data fragments is grouped into a container object in sequential order. Each encoded data fragment is a specific fragment size, and the container object is a specific container object size. The sequential order of the set of encoded data fragments can be tracked in a log in memory, such that the location of any one of the data fragments in the container object can be determined. The container object can be stored directly on a specific backend storage element, without using a file system. A corresponding container object identifier identifies the physical storage location of the container object on the backend storage element. The container object identifier is tracked in the log in memory, such that the physical location on the backend storage element of any specific one of the set of encoded data fragments in the container object can be determined.

A waveform data structure includes a plurality of types of frames having different data sizes. Each of the plurality of types of frames includes an auxiliary information area and a data area. The auxiliary information area includes an area for storing common effective-bit length data for a section of waveform samples, and an area for storing an identifier for identifying one of the plurality of types of frames. The data area is an area for storing extracted waveform samples which are extracted from the waveform samples based on the common effective-bit length. The number of the extracted waveform samples is determined based on the common effective-bit length.

A method for scanning for flaws on a magnetic recording medium is disclosed. The magnetic recording medium has a first set of nonconsecutive data tracks and a second set of nonconsecutive data tracks. The method includes writing a test pattern to only the first set of nonconsecutive data tracks of the magnetic recording medium, reading of the test pattern written to the first set of nonconsecutive data tracks, and identifying flaws within the first set of nonconsecutive data tracks and the second set of nonconsecutive data tracks based on the reading the test pattern.