Abstract: Methods and devices for coherent holographic data channel techniques. Coherent techniques for data detection generally include homodyne and heterodyne detection. Techniques for quadrature homodyne detection, resampling quadrature homodyne detection, n-rature homodyne detection, and spatial wavefront demodulation. Coherent detection techniques in turn enable coherent channel modulation techniques such as phase modulation (including binary phase shift keying, or BPSK; phase quadrature holographic multiplexing, or QPSK; and quadrature amplitude modulation, or QAM). Coherent detection may also enable or improve the performance of other channel techniques such as partial response maximum likelihood (PRML), the various classes of extended PRML, and of noise-predictive maximum likelihood (NPML) detection.

Abstract: Methods and devices for coherent holographic data channel techniques are presented. Coherent techniques for data detection generally include homodyne and heterodyne detection. Techniques for quadrature homodyne detection, resampling quadrature homodyne detection, n-rature homodyne detection, and spatial wavefront demodulation are presented. Coherent detection techniques in turn enable coherent channel modulation techniques such as phase modulation (including binary phase shift keying, or BPSK; phase quadrature holographic multiplexing, or QPSK; and quadrature amplitude modulation, or QAM). Coherent detection may also enable or improve the performance of other channel techniques such as partial response maximum likelihood (PRML), the various classes of extended PRML, and of noise-predictive maximum likelihood (NPML) detection.

Abstract: Methods and devices for coherent holographic data channel techniques are presented. Coherent techniques for data detection generally include homodyne and heterodyne detection. Techniques for Quadrature homodyne detection (QHD), Enhanced resampling quadrature homodyne detection (ERQHD), N-rature homodyne detection (NHD), and local oscillator fringe demodulation are presented. Coherent detection techniques in turn enable coherent channel modulation techniques such as phase modulation (including binary phase shift keying, or BPSK; phase quadrature holographic multiplexing, or QPSK; and quadrature amplitude modulation, or QAM). Coherent detection may also enable or improve the performance of other channel techniques such as Partial response maximum likelihood (PRML), the various classes of extended PRML, and of Noise predictive maximum likelihood (NPML) detection.

Abstract: A disk drive comprising a rotatable disk, a head actuated over the disk, and a controller is disclosed. The controller is configured to write data on the disk using the head, to store logical-to-physical mapping information for data already written on the disk in a circular buffer as the data is written on the disk, and to write a plurality of metadata files on the disk using the head, wherein the plurality of metadata files are interspersed with the data on the disk and each of the metadata files includes contents of the circular buffer at a time the metadata file is written on the disk.

Abstract: Managing data objects in a Data Storage Device (DSD) including a disk and a volatile memory for storing data. A data object is written from the volatile memory in a data object zone of the disk of the DSD. At least one most recent version of a previously written data object is rewritten in the data object zone so that an earlier version of the data object written from the volatile memory does not interrupt a contiguous plurality of most recent versions of data objects stored in the data object zone.

Abstract: A disk drive is disclosed that utilizes an additional address mapping layer between logical addresses used by a host system and physical locations in the disk drive. Physical locations configured to store metadata information can be excluded from the additional address mapping layer. As a result, a reduced size translation table can be maintained by the disk drive. Improved performance, reduced costs, and improved security can thereby be attained.

Abstract: A data storage device is disclosed including a non-volatile media having a plurality of physical locations for storing user data, each physical location associated with a logical block address (LBA), a translation table having a plurality of entries, each entry having a mapping of one or more LBAs to a corresponding number of physical locations on the non-volatile media. The data storage device further includes control circuitry that divides the translation table into a plurality of segments, each segment including a group of entries corresponding to a range of LBAs, determines a first score for each segment using a first metric, and selects a segment for defragmentation by utilizing the first score for each segment.

Abstract: The present invention relates to methods and systems for efficiently accessing data stored on a data storage device. The data storage device may comprise various types of media, such as shingled media and non-shingled media, alone or in combination. The data storage device may employ a logical block address space for specifying location of blocks of data stored on the data storage device. In addition, pre-determined sequential ranges of logical block addresses are grouped together and may be referenced collectively. In some embodiments, each type of media type may be partitioned into sections for containing different sizes of collections. Each collection of logical block addresses may be allocated to an arbitrary logical slot. Each logical slot may then be linked to a physical slot on the data storage device.

Abstract: A disk drive is disclosed comprising a head actuated over a rotatable disk. A write operation is processed to write data on the disk using the head, wherein prior to writing the data on the disk, logical-to-physical mapping information is stored in a circular buffer, wherein the logical-to-physical mapping information identifies locations on the disk to write the data. A plurality of metadata files are written on the disk using the head, wherein the plurality of metadata files are interspersed with the data on the disk and each of the metadata files includes contents of the circular buffer at a time the metadata file is written on the disk. When the write operation is aborted, the logical-to-physical mapping information in the circular buffer is modified to identify the locations on the disk actually written.

Abstract: A disk drive subsystem is disclosed that implements a process for metadata recovery. Certain embodiments relate to recovery of metadata containing information indicating the physical locations in the disk drive in which host data is stored. In an embodiment, the metadata to be recovered is disposed in sequence with, or in physical association with host data that it describes. Recovery is accomplished by identifying metadata that is valid, but is absent from one or more translation tables containing translation information. Metadata portion can include one or more identifiers that are sequentially related to identifiers included in one or more other metadata portions. Performance improvements can thereby be attained.

Abstract: Apparatus and method for positioning a head adjacent tracks on a recording surface in a disc drive. A servo control circuit includes a multi-mode servo position error signal (PES) demodulator circuit having an operand generator which outputs operand values from decoded servo position data transduced by the head from the disc surface, and a PES generator which generates a PES indicative of head position with respect to the disc surface in accordance with a selected PES mode from a population of mutually exclusive PES modes each derived from a different combination of selected operand values. A programmable servo processor outputs a current adjustment signal to adjust the current applied to an actuator motor in relation to the PES and a desired position. The servo processor selectably configures the PES generator for each track so that different PES modes are used for different tracks.

Abstract: Apparatus and method which provide accelerated servo control value calculations for a control processor controlling an actuator maintaining a head adjacent a rotatable disc f a disc drive. A dedicated multiply-accumulate hardware core of a servo micro engine calculates sum-of-products terms common in servo control loops. The multiply-accumulate hardware core uses a pipeline with stages for fetch, read, multiply, accumulate, and write-back as an arithmetic core to fully utilize all of the hardware during every servo interval. Feeding this arithmetic core is a dedicated state memory, from which a first signed servo state and a second signed servo state are read and where calculation results may be optionally written. Another, independent, coefficient memory provides predetermined coefficients used in resolving servo control loop algorithms. A final dedicated instruction memory provides shifter control values and the addresses of the states and coefficients.

Abstract: A data storage system and method of scheduling commands in such a data storage system are provided in which commands are stored in a command sort queue and a scheduled command queue. Commands in the command sort queue are sorted and assigned a priority. Eventually, commands in the command sort queue are transferred to the scheduled command queue. Commands in the scheduled command queue are executed without further sorting. The desired queue depth or size of the scheduled command queue is determined as a function of both the queue depth of the command sort queue and a command execution rate value which is indicative of the rate at which commands in the scheduled command queue are executed. The desired queue depth may be dynamically determined using the queue depth of the command sort queue and the command execution rate value as inputs to a look-up table. The data storage system may include a small computer system interface (SCSI) disc (or “disk”) drive which executes commands from a host system.