International Business Machines Corporation

Robert Yuan-Shih Li

Peter Cheng-I Fang

Christopher William Bergevin

Hoan Andrew Au

Albert Shou-Chi Su

Carol Inouye Chiu

Xiang-Jun (Leon) Feng

Hard biasing of a magnetoresistive sensor or a spin valve sensor in a magnetic read head is initialized by repeatedly applying a magnetic field to the hard biasing at any level of fabrication of the magnetic read head or any combination of levels of fabrication of the read head such as at the wafer level, row bar level, single slider level, head gimbal assembly (HGA) level and/or head stack assembly (HSA) level.

Method of initializing hard bias of a magnetic read head

A method and apparatus for compensating for multiple thermal asperity events in a sector. The present invention provides for the detection, recording and recovery from errors caused by multiple thermal asperities occurring in a single sector. The method includes detecting thermal asperity events in a sector, setting a flag indicating each occurrence of a thermal asperity event in the sector, maintaining a count of the detected thermal asperity events in the sector and recording a byte location for each of the detected thermal asperity events in the sector. The method further includes performing a data recovery procedure in response to the detected thermal asperity events. The data recovery procedure is performed using the flag settings and a location corresponding to the detected thermal asperity events. The data recovery procedure is performed using the count of the detected thermal asperity events. The setting of a flag includes setting a bit in a register. The setting of a bit indicates a start byte location for a thermal asperity event. The maintaining a count of the detected thermal asperity events in the sector includes the setting of a bit in the register for each detected thermal asperity event, the count being equal to a number of bits set in the register. The recording a location for each of the detected thermal asperity events in the sector includes setting a bit in a register, the bit position being associated with the location of the asperity event. The maintaining a count of the detected thermal asperity events in the sector includes setting a bit in a register for each detected thermal asperity events, the count being equal to a number of bits set in the register.

Method and apparatus for detecting, logging and recovering from errors caused by multiple thermal asperities in a sector

A method in a data processing system for minimizing read/write errors caused by impaired performance of a hard disk drive during runtime operation of the hard disk drive. The runtime operation includes an active mode during which read/write operations are conducted and a standby mode which occurs while no read/write operation is underway. First, at least one performance parameter of a hard disk drive is monitored during a standby mode of operation. Next, in response to detecting a degraded value of the at least one performance parameter, performing preventive recovery action only during the standby mode of operation, such that the performance parameter is restored to an acceptable value without interfering with hard disk drive operation during an active mode.

Preventive recovery action in hard disk drives

A system to control the interior temperature and particularly the slider and disk temperature of hard disk drives that utilizes the spindle motor to spin a fanning structure. The fanning structure is preferably integrated into the hard disk drive and initiates a cooling air stream that is directed within the contained interior of the hard disk drive toward a Peltier-element that drains the thermal energy into the surrounding environment. In an alternate embodiment, the fanning structure initiates an exterior air stream that provides a cooling air stream at the outside of the Peltier-element. The Peltier-element is controllable to decouple operational temperature variations from environmental temperature variations.

Heat dissipation system of magnetic recording disk

A method and apparatus for providing amplitude instability data recovery for AMR/GMR heads during amplitude loss using MSE and/or amplitude envelope detection procedures. The method includes (a) initiating a data recovery procedure by selecting a detection mode for detecting when an error condition occurs, (b) performing the selected detection mode, (c) determining a reset action for resetting the magnetic head, (d) performing the reset action to reset the magnetic head and (f) re-reading data in the track after performing the reset action. An embodiment of the invention further includes (g) determining whether the resetting of the magnetic head allowed recovery of the data in the track and (h) terminating the data recovery procedure when the data is recovered. An embodiment of the invention further includes (i) determining whether predetermined limits have been exhausted when the data is not recovered, (j) terminating the data recovery procedure when the predetermined limits have been exhausted and repeating steps (a)-(g) when the predetermined limits have not been exhausted. In an embodiment of the invention, the determining a reset action for resetting the magnetic head further includes applying a maximum write current to the head, toggling a head bias current, toggling the head bias current and the write current, or applying a reset pulse to the head.

Method and apparatus for providing amplitude instability data recovery for AMR/GMR heads

A method and system for detecting common mode disturbances from a magnetic recording head having dual magnetic recording elements. An electrical current is supplied to both of the dual magnetic recording elements within the magnetic recording head. Thereafter, the electrical current is shunted through only one of the dual magnetic recording elements. A voltage signal is then detected across the dual magnetic recording elements, which occurs in response to the shunting of the electrical current through only one of the dual magnetic recording elements. Finally, the voltage signal is analyzed for indications of common mode disturbances accentuated as a result of the shunting of the electrical current through only one of the dual magnetic recording elements. Common mode disturbances that can be detected include thermal asperities.

Method and system for detecting common mode disturbances from a dual

A data recovery scheme is disclosed wherein a majority voting scheme arrives at the correct data and resolves ties with a minimum number of reads. The method includes reading at least one instance of data including a first set of ECC checkbytes from a media, each instance of data and ECC checkbytes comprising a string of bits, forming a voting data string from a majority value for each bit position in the string of bits, generating a second set of ECC checkbytes using the voted data string and returning the voted data sting to a host if the second set of ECC checkbytes is equal to the first set of ECC checkbytes.

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Fremont, CA, United States of America

Robert Yuan-Shih Li