Abstract: Embodiments of the present invention provide a magnetic disk drive in which the error correction capability of ECC is improved without sacrificing the storage capacity. In one embodiment, a data track adopts a format structure in which no data-to-data gap area is formed in data sectors. When one of the data sectors is updated in a state in which the rotational speed of a magnetic disk does not satisfy specified conditions, a leading end area of a succeeding data sector or a trailing end area of a preceding data sector is overwritten by the data sector. If a read error occurs in the overwritten data sector, ERP steps are executed to perform read retry so that the read error is recovered by means of on-the-fly ECC or erasure correction. In the case of the erasure correction, an erasure pointer equivalent to the maximum number of overwritten bytes is set.

Abstract: Embodiments in accordance with the present invention relate to detecting a micro-relief that exists on surfaces of a magnetic disk. A phase or frequency of a read signal obtained when data written to a minute projection or a minute concavity on a recording surface of a magnetic disk is read out, differs from that of a read signal obtained when data written to a flat recording surface is read out. The phase progresses in the minute projection, whereas the phase is delayed in the minute concavity. A micro-relief is detected by measuring a deviation value of this frequency, and then defect registration is performed. Embodiments in accordance with the present invention are configured to detect a minute projection whose level does not cause TA. Embodiments in accordance with the present invention may also be configured to provide a highly reliable magnetic disk drive by controlling the flying height in response to a state of a minute projection and that of a minute concavity.

Abstract: Embodiments of the invention provide a magnetic disk drive capable of reducing an area used for a preamble of each data sector to increase the storage capacity. The magnetic disk drive adopts a data-surface servo system. In one embodiment, main preambles are written on a magnetic disk at a frequency of a data clock. Each of data sectors is written with a write clock that is synchronized with a signal obtained by reading the main preamble. The data sectors include sub preambles respectively. When the data sector which has been written in this manner is read, a read clock is synchronized by use of a signal obtained by reading the main preamble, and a signal obtained by reading the sub preamble included in a data sector to be read. The bit length of the sub preamble is shorter than that of the conventional preamble that is used to independently achieve the synchronization.

Abstract: Embodiments of the invention provide a magnetic disk drive and its control method capable of effectively using the unrecordable area which is caused due to the composite magnetic head's gap between the read head and the write head. In one embodiment, a disk drive comprises a composite magnetic head structured in such a manner that during write the write head WH reaches each servo area earlier than the read head RH, and a read write control unit to control the write and read done by the composite magnetic head. On the disk, common servo data SP to be used both during read and during write, write servo data SW to be used during write and read servo data SR to be used during read are recorded in this order in each servo area. During write, the read write control unit starts the write head recording data at the timing when reading write servo data SW from the servo area is completed.

Abstract: Embodiments of the invention detect a head offset in a data region between servo regions in a data write operation. To detect a head offset even in a data region between servo regions, a magnetic disk drive according to an embodiment of the invention makes adjustments to maintain a fixed relative position between the write head and the read head and reads positional information embedded in certain data by use of the read head until just before writing data. This allows the magnetic disk drive to detect a head offset until just before writing data, leading to enhanced reliability.

Abstract: Embodiments in accordance with the present invention relate to detecting a micro-relief that exists on surfaces of a magnetic disk. A phase or frequency of a read signal obtained when data written to a minute projection or a minute concavity on a recording surface of a magnetic disk is read out, differs from that of a read signal obtained when data written to a flat recording surface is read out. The phase progresses in the minute projection, whereas the phase is delayed in the minute concavity. A micro-relief is detected by measuring a deviation value of this frequency, and then defect registration is performed. Embodiments in accordance with the present invention are configured to detect a minute projection whose level does not cause TA. Embodiments in accordance with the present invention may also be configured to provide a highly reliable magnetic disk drive by controlling the flying height in response to a state of a minute projection and that of a minute concavity.

Abstract: Embodiments of the invention provide a magnetic disk drive capable of reducing an area used for a preamble of each data sector to increase the storage capacity. The magnetic disk drive adopts a data-surface servo system. In one embodiment, main preambles are written on a magnetic disk at a frequency of a data clock. Each of data sectors is written with a write clock that is synchronized with a signal obtained by reading the main preamble. The data sectors include sub preambles respectively. When the data sector which has been written in this manner is read, a read clock is synchronized by use of a signal obtained by reading the main preamble, and a signal obtained by reading the sub preamble included in a data sector to be read. The bit length of the sub preamble is shorter than that of the conventional preamble that is used to independently achieve the synchronization.

Abstract: Embodiments of the present invention provide a magnetic disk drive in which the error correction capability of ECC is improved without sacrificing the storage capacity. In one embodiment, a data track adopts a format structure in which no data-to-data gap area is formed in data sectors. When one of the data sectors is updated in a state in which the rotational speed of a magnetic disk does not satisfy specified conditions, a leading end area of a succeeding data sector or a trailing end area of a preceding data sector is overwritten by the data sector. If a read error occurs in the overwritten data sector, ERP steps are executed to perform read retry so that the read error is recovered by means of on-the-fly ECC or erasure correction. In the case of the erasure correction, an erasure pointer equivalent to the maximum number of overwritten bytes is set.

Abstract: Embodiments of the invention provide a magnetic disk drive and its control method capable of effectively using the unrecordable area which is caused due to the composite magnetic head's gap between the read head and the write head. In one embodiment, a disk drive comprises a composite magnetic head structured in such a manner that during write the write head WH reaches each servo area earlier than the read head RH, and a read write control unit to control the write and read done by the composite magnetic head. On the disk, common servo data SP to be used both during read and during write, write servo data SW to be used during write and read servo data SR to be used during read are recorded in this order in each servo area. During write, the read write control unit starts the write head recording data at the timing when reading write servo data SW from the servo area is completed.

Abstract: Embodiments of the invention detect a head offset in a data region between servo regions in a data write operation. To detect a head offset even in a data region between servo regions, a magnetic disk drive according to an embodiment of the invention makes adjustments to maintain a fixed relative position between the write head and the read head and reads positional information embedded in certain data by use of the read head until just before writing data. This allows the magnetic disk drive to detect a head offset until just before writing data, leading to enhanced reliability.