Western Digital Technologies, Inc.

Maxtor Corporation

Seagate Technology Incorporated

Vmware, Inc.

Hitachi Global Storage Technologies Netherlands B.v.

Wei Guo

Guoxiao Guo

Lin Guo

Michael A Chang

Jie Yu

Xiaoping Hu

Russ A Quisenberry

Jifang Tian

Yunfeng Li

David Marcus Tung

Jiangang Liang

Jianguo Zhou

Richard Koonwai Wong

Mark Heimbaugh

William Flynn

Erhard Theodor Schreck

Yuan Chen

Siri S Weerasooriya

Yu Sun

Jack M Chue

Yih-Jen Dennis Chen

Brian P Rigney

Charles A Park

Da Wan

Donald Joseph Brunnett

Jenghung Chen

Abhishek Dhanda

John Edward Scura

Carl E Barlow

Min Chen

Richard Oswald

Yang Ping

Sanghoon Chu

Bill S Wang

Xiaokun L Chew

Yiming Chen

Yanchu Xu

Jong-Ming Lin

Oliver W Northrup

Mark S Seymour

Yun Hong

Aravinda Kidambi Srinivasan

Yanjun Lin

Tim Glassburn

Michael Hatch

Steven C Smith

Harold Vinson Chao Lim

Ge Xu

William M Marvin, Jr

Leonid Ryzhyk

Deepika Rajendra Kalani

Jui Yi Kao

Jiayu Yu

Yuanjun Yao

Mihir Patil

Various apparatuses, systems, methods, and media are disclosed to provide a heat-assisted magnetic recording (HAMR) medium that includes a sacrificial layer and corresponding etching processes to minimize head to media spacing. The medium may include the sacrificial layer and a capping layer where each of the layers is etched to reduce roughness. The sacrificial layer is configured to ensure an etch rate that allows for selective etching and may be deposited on the capping layer and after etching, may remain along grain boundaries of the capping layer. The remaining portions of the sacrificial layer may form a discontinuous layer, including layer segments positioned along grain boundaries of the capping layer. The sacrificial layer may be made of non-magnetic materials different from the materials of the capping layer or materials of an overcoat layer deposited on the etched capping layer.

Magnetic recording media with sacrificial layer and corresponding etching processes to minimize head to media spacing

Example methods and systems for software bug reproduction. One example method may comprise obtaining log information associated with multiple transactions processed by a control-plane node to configure a set of data-plane nodes and transform an initial network state to a first network state; and configuring a replay environment that is initialized to the initial network state, and includes a mock control-plane node and a set of mock data-plane nodes. The method may also comprise, based on the log information, replaying the multiple transactions using the mock control-plane node to configure the set of mock data-plane nodes and transform the replay environment from the initial network state to a second network state. Based on a comparison between the first network state and the second network state, a determination may be made as to whether a software bug is successfully reproduced in the replay environment.

Software bug reproduction

Example methods and systems for routing domain computation are described. In one example, a computer system may assign multiple logical entities with respective routing domain identifiers (IDs) by processing network topology information using multiple compute nodes. In response to detecting a network topology change associated with a particular logical entity, the computer system may determine first state change information identifying a first update to first state information maintained by a first compute node; and second state change information identifying a second update to second state information maintained by a second compute node. Further, the particular logical entity with an updated routing domain ID based on the first state change information and the second state change information. The updated routing domain ID may be used in a communication between a management entity and host(s) supporting the particular logical entity.

Incremental and parallel routing domain computation

A disk drive is disclosed comprising a head actuated over a disk comprising a plurality of tracks defined by servo sectors forming a plurality of full wedges and a plurality of mini wedges. The wedge ID field of a servo sector forming one of the full wedges is offset from a beginning of a sync mark by a first offset, and the wedge ID field of a servo sector forming one of the mini wedges is offset from the beginning of the sync mark by a second offset equal to the first offset. A first servo sector is read from the disk to generate a read signal, the read signal is demodulated to detect the wedge ID of the first servo sector, and the detected wedge ID is evaluated to determine whether the first servo sector forms one of the mini wedges.

Disk drive detecting mini wedge by evaluating wedge ID of servo sector

A disk drive is disclosed comprising a timing loop configured to generate a clock synchronized to a rotation of a disk and a servo loop configured to control an actuator to actuate a head over the disk. A timing signal generated by the timing loop is filtered with a pre-compensation filter (PCF) comprising an inverse transfer function from a delta in a rotation velocity of the disk (&#x394;&#x3c9;) due to a vibration affecting the disk drive to the timing signal, and the actuator is controlled to actuate the head over the disk based on an output of the PCF.

Disk drive using timing loop control signal for vibration compensation in servo loop

A data storage device is disclosed comprising a first head actuated over a first disk surface comprising servo tracks defined by full servo sectors, and a second head actuated over a second disk surface comprising servo tracks defined by mini servo sectors. At least part of a track address is read from one of the full servo sectors to generate at least one high order bit of a full track address, and at least part of a track address is read from one of the mini servo sectors to generate at least one low order bit of the full track address. The high order bit and the low order bit are combined to generate at least part of the full track address, and during an access of the second disk surface, the second head is servoed over the second disk surface based on the full track address.

Data storage device employing full servo sectors on first disk surface and mini servo sectors on second disk surface

A data storage device is disclosed comprising a disk comprising data, and a head actuated over the disk. A timing signal is generated by reading the data from the disk, and a frequency generator is adjusted based on the timing signal to generate a disk locked clock substantially synchronized to a rotation speed of the disk. A free fall condition is detected based on the timing signal, and when the free fall condition is detected the head is parked.

Data storage device detecting free fall condition from disk speed variations

A data storage device is disclosed comprising a disk surface comprising a plurality of tracks, wherein each track comprises a plurality of data sectors and a plurality of servo sectors. The data storage device further comprises a head actuated over the disk surface, the head comprising at least one read element and at least one write element. Control circuitry is configured to use the head to write to a first data sector on the disk surface while simultaneously reading from a first servo sector on the disk surface.

Data storage device reading servo sector while writing data sector

A disk drive is disclosed comprising a head actuated over a disk comprising a plurality of servo tracks defined by full sectors and intervening short servo sectors, where each full servo sector comprises a preamble, a sync mark, and servo bursts, and each short servo sector comprises a reference pattern and servo bursts. A first phase error is generated based on the sync mark in a first full servo sector, and a disk locked clock is adjusted in response to the first phase error. A second phase error is generated based on the reference pattern in a first short servo sector, and the second phase error is processed to determine whether the disk locked clock slipped a cycle before the head reaching the first short servo sector.

Disk drive compensating for cycle slip of disk locked clock when reading mini-wedge

A disk drive is disclosed comprising a disk and a head actuated over the disk. A burst metric is generated in response to a burst read signal. The burst metric comprises at least one of an alpha metric comprising a ratio of a first burst amplitude of a first phased based servo burst measured at a first radial offset to a second burst amplitude of a second phased based servo burst measured at a second radial offset, a harmonic metric comprising a ratio of a first harmonic of the burst read signal as the head is moved radially over the disk to a higher harmonic of the burst read signal as the head is moved radially over the disk, and a spiral track crossing metric comprising a first and second interval each representing a partial duration of the read element crossing a spiral track.

Disk drive evaluating burst metric

A data storage device is disclosed comprising a first disk surface comprising servo tracks defined by servo sectors and recorded at a first radial density, and a first head actuated over the first disk surface. A servo sector on the first disk surface is read to generate a first physical position measurement that is converted into a first virtual position measurement corresponding to a nominal radial density of servo tracks different from the first radial density. The first head is servoed over the first disk surface based on the first virtual position measurement.

Data storage device servoing heads based on virtual servo tracks

A data storage device is disclosed comprising a head actuated over a disk comprising a plurality of servo sectors defining a plurality of servo tracks. The servo tracks form a plurality of servo zones, and at least one servo sector of a servo track comprises a partial track address. A read signal generated by the head is processed to detect a current servo zone for the head, and the read signal is processed to detect the partial track address in one of the servo sectors of the current servo zone. A full track address is generated based on the detected servo zone and the detected partial track address.

Data storage device estimating servo zone to reduce size of track address

A disk drive is disclosed comprising a disk comprising servo data, and a head actuated over the disk. An offset rrepresenting a difference between an axial rotation of the disk and an axial rotation of the servo data is estimated, and radial dependent timing compensation values are generated in response to the estimated r. A phase error is generated in response to the servo data, and a control signal is generated in response to the phase error and the radial dependent timing compensation values. A frequency of an oscillator is adjusted in response to the control signal.

Disk drive generating a disk locked clock using radial dependent timing feed-forward compensation

A disk drive is disclosed comprising a head actuated over a disk comprising a plurality of spiral tracks, wherein each spiral track comprising a high frequency signal interrupted at a predetermined interval by a sync mark. An offset rrepresenting a difference between an axial rotation of the disk and an axial rotation of the spiral tracks is estimated. Radial dependent timing compensation values are generated in response to the estimated r. A phase error is generated in response to the sync marks in the spiral track crossings. A control signal is generated in response to the phase error and the radial dependent timing compensation values, and a frequency of an oscillator is adjusted in response to the control signal.

Disk drive servo writing from spiral tracks using radial dependent timing feed-forward compensation

A disk drive is disclosed comprising a head actuated over a disk comprising a plurality of servo sectors defining a plurality of servo tracks, wherein the servo tracks form a plurality of servo zones, and a servo data rate of servo sectors in a first servo zone is different than a servo data rate of servo sectors in a second servo zone. A disk locked clock is synchronized to the data rate of the servo sectors in the first servo zone, wherein the disk locked clock for generating a timing window relative to the servo sectors. When the head crosses from the first servo zone to the second servo zone, at least one of the disk locked clock and the timing window is adjusted to compensate for a timing transient.

Disk drive adjusting servo timing to compensate for transient when crossing a servo zone boundary

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Fremont, CA, United States of America

Wei Guo