Abstract: A two-dimensional magnetic recording (TDMR) disk drive has a disk with servo tracks with a track pitch that varies across the radius of the disk. The servo track pitch (STP) is related to the cross-track spacing (CTS) of the multiple read sensors in the TDMR head structure. The CTS is given by the equation: CTS=(CTO)cos ?+(ATO)sin ?, where ? is the skew angle, and CTO is the cross-track spacing and ATO the along-the-track spacing of the read sensors at zero skew angle. The optimal variable STP profile results in track misregistration reduction because it allows each read sensor to read a different servo half-track and thus noise sources not correlated to noise sources read by the other read sensors. The servo tracks may be arranged into a plurality of annular bands, with the STP in each band being fixed and different from the STP in the other bands.

Abstract: Disk drives are described that include a hybrid servo patterns in which the augmented servo burst fields, which can be Integrated Servo sequences, that provide the PES and also supply additional information such as a SAM, LSBs of the track identifier (TID), sector number, depending on the specific embodiment. Embodiments without write-to-read gaps before the servo sector SIDs are described. The augmented servo burst fields can be read after gapless writing of the preceding data area. For seeking operations the needed bits of the TID without having to detect or decode the Integrated Servo sequences or other augmented servo burst fields. Depending on the embodiment all or the most significant bits of the track identifier can be obtained during seeks by reading the TID fields passing under a read head as the read head moves across tracks without having to detect or decode the Integrated Servo sequences.

Abstract: A disk drive is described with a single servo master timer that is used to control timing critical signals such as servo gate, SAM windows, channel power save, PREAMP power save and so on. The master timer is adjusted to compensate for SAM detection errors (early, late or missed) and provides improved servo timing quality. In an embodiment the adjustable master timer can be selectably clocked by either the DLC/DSW clock or the system clock.

Abstract: Disk drives are described that include a hybrid servo patterns in which the augmented servo burst fields, which can be Integrated Servo sequences, that provide the PES and also supply additional information such as a SAM, LSBs of the track identifier (TID), sector number, depending on the specific embodiment. Embodiments without write-to-read gaps before the servo sector SIDs are described. The augmented servo burst fields can be read after gapless writing of the preceding data area. For seeking operations the needed bits of the TID without having to detect or decode the Integrated Servo sequences or other augmented servo burst fields. Depending on the embodiment all or the most significant bits of the track identifier can be obtained during seeks by reading the TID fields passing under a read head as the read head moves across tracks without having to detect or decode the Integrated Servo sequences.

Abstract: A disk drive is described with a single servo master timer that is used to control timing critical signals such as servo gate, SAM windows, channel power save, PREAMP power save and so on. The master timer is adjusted to compensate for SAM detection errors (early, late or missed) and provides improved servo timing quality. In an embodiment the adjustable master timer can be selectably clocked by either the DLC/DSW clock or the system clock.

Abstract: Disk drives are described in which the conventional write-to-read gap is omitted in selected sectors which frees up space that can be used for other purposes including writing a higher number of bits in the user data area in the gapless selected sectors. Alternative embodiments can use the additional space for servo information such as a repeatable run out (RRO) field. Conventional servo sector SID formats can be used for both gapped and gapless SIDs, which means that during seeking and reading operations full SIDs can be read for every wedge. The tradeoff for being able to write data much closer to the gapless SIDs is that the servo system does not detect the SAM or read the TID in the gapless SIDs during write operations.

Abstract: A method according to one embodiment comprises detecting a change in a rotational velocity of a magnetic disk or a spindle coupled to the magnetic disk, the change being caused by head-disk contact. A method for detecting head-disk contact according to another embodiment comprises measuring a rotational velocity of a magnetic disk or a spindle coupled to the magnetic disk; detecting a change in the rotational velocity, the change being caused by head-disk contact; and correlating the change in rotational velocity with the head-disk contact.

Abstract: A method according to one embodiment comprises detecting a change in a rotational velocity of a magnetic disk or a spindle coupled to the magnetic disk, the change being caused by head-disk contact. A method for detecting head-disk contact according to another embodiment comprises measuring a rotational velocity of a magnetic disk or a spindle coupled to the magnetic disk; detecting a change in the rotational velocity, the change being caused by head-disk contact; and correlating the change in rotational velocity with the head-disk contact.

Abstract: A self-servowriting (SSW) method that, with the actuator fully engaged against a compliant structure (e.g., a crashstop), first writes a tightly-spaced open-loop sequence of servo bursts in a segmented spiral path and then continues writing this tightly-spaced sequence under closed-loop servo control while reading back amplitude information from the servo bursts written earlier until the tightly-spaced burst pattern extends over several read-write head (RWH) offset intervals. With the actuator still engaged against the compliant structure, this tightly-spaced startup sequence is then read back by the closed servo control loop to write a number of concentric servo seed tracks, which are then self-propagated across the remainder of the disk surface to produce a final servopattern.

Abstract: A self-servowriting (SSW) method that, with the actuator fully engaged against a compliant structure (e.g., a crashstop), first writes a tightly-spaced open-loop sequence of servo bursts in a segmented spiral path and then continues writing this tightly-spaced sequence under closed-loop servo control while reading back amplitude information from the servo bursts written earlier until the tightly-spaced burst pattern extends over several read-write head (RWH) offset intervals. With the actuator still engaged against the compliant structure, this tightly-spaced startup sequence is then read back by the closed servo control loop to write a number of concentric servo seed tracks, which are then self-propagated across the remainder of the disk surface to produce a final servopattern.

Abstract: A method and apparatus for controlling write operations for a data storage system during and after a shock event is disclosed. A shock sensor measures the magnitude of a shock event and compares the magnitude of the shock event to at least two predetermined thresholds. Write operations are then inhibited based upon the comparison of the magnitude of the shock event and the at least two predetermined thresholds. When the shock event meets a first upper threshold, the write is inhibited until the write is requalified. The write is executed if the measured shock event does not meet a second lower threshold and the write is paused for a predetermined time period when the measured shock event meets the second lower threshold but does not meet the first upper threshold.

Abstract: A method and apparatus for controlling write operations for a data storage system during and after a shock event is disclosed. A shock sensor measures the magnitude of a shock event and compares the magnitude of the shock event to at least two predetermined thresholds. Write operations are then inhibited based upon the comparison of the magnitude of the shock event and the at least two predetermined thresholds. When the shock event meets a first upper threshold, the write is inhibited until the write is requalified. The write is executed if the measured shock event does not meet a second lower threshold and the write is paused for a predetermined time period when the measured shock event meets the second lower threshold but does not meet the first upper threshold.