A method of operating a storage device includes reading data from a storage medium using a detector, processing signals from the detector through a plurality of processing circuits, each respective processing circuit in the plurality of processing circuits being optimized for a different state of a channel condition and providing a respective output metric, selecting a processing circuit from the plurality of processing circuits by comparing the respective output metrics from each processing circuit in a predetermined manner, and designating as output of the detector output of the processing circuit that is selected. The output metrics may be branch metrics or path metrics, and the channel condition may be fly-height or phase shift. The storage device includes a storage medium, and a read channel including a detector, and processing circuits that process signals from the detector. Each respective processing circuit is optimized for a different state of a channel condition.

According to one embodiment, a magnetic disk device includes a magnetic disk including at least one servo zone that includes a first data storage track with a first servo pattern having a first frequency and a second data storage track with a second servo pattern having a second frequency, wherein the first data storage track is located closer to an outer diameter of the magnetic disk than the first data storage track and the first frequency is greater than the second frequency; a magnetic head that faces the magnetic disk; and a zone servo switching unit that switches a servo pattern frequency employed to position the magnetic head in a radial direction based on a radial position of the magnetic head.

A method according to one embodiment includes generating a y-position estimate based on a servo readback signal from a servo reader reading a servo band, retrieving or calculating a nonlinearity-correction value corresponding to the y-position estimate, adjusting the y-position estimate using the nonlinearity-correction value, and outputting the adjusted y-position estimate. A computer program product for compensating for nonlinearity in a timing based servo pattern according to one embodiment includes a computer readable storage medium having program instructions embodied therewith. The computer readable storage medium is not a transitory signal per se. The program instructions are readable and/or executable by a controller to cause the controller to perform the foregoing method.

According to one embodiment, a position detecting device includes a detecting portion which periodically detects a plurality of pieces of information generated in accordance with positional information divided into upper digits and lower digits. The upper digits are further divided into a plurality of pieces of upper digit information equal to the number of the period. The pieces of the upper digit information are obtained in a predetermined order. The lower digits are obtained simultaneously with any one of the pieces of the upper digit information. The positional information is divided so that the number of values, which are obtainable in one piece of the upper digit information provided by dividing the upper digits, and a division number of the upper digits are coprime.

According to one embodiment, servo patterns different in servo pattern frequency are recorded in zones divided in a radial direction on a magnetic disc, and the servo patterns in the adjacent zones overlap each other in a predetermined area from a zone servo boundary between the zones, and a determination boundary where it is determined to execute a crossing process is set within the overlapping area of the servo patterns upstream from the zone servo boundary, based on position information on a seek destination and the present position of the magnetic head.

The magnetic tape includes a non-magnetic support, and a magnetic layer containing a ferromagnetic powder. A magnetic tape cartridge and a magnetic tape apparatus include the magnetic tape. Sci obtained by measuring a surface of the magnetic layer with an atomic force microscope and by Equation A is 1.40 or more and 1.60 or less, and standard deviation of the Sci in a width direction of the surface of the magnetic layer is 0.05 or less. In Equation A, Sq is a root-mean-square height Sq specified in ISO 25178, Vv(h.sub.0.05)-Vv(h.sub.0.8) is a void volume in a region where a load area ratio in a bearing curve is 5% or more and 80% or less, and A is a measurement region area.

[00001]$\begin{array}{cc}\mathrm{Sci}=\left(\frac{\mathrm{Vv}\left(h_{0.05}\right)-\mathrm{Vv}\left(h_{0.8}\right)}{A}\right)/\mathrm{Sq}& \mathrm{Equation}A\end{array}$

The magnetic tape includes a non-magnetic support, and a magnetic layer containing a ferromagnetic powder. A magnetic tape cartridge and a magnetic tape apparatus include the magnetic tape. A protruding peak height Spk specified in ISO 25178 on a surface of the magnetic layer is 1.5 nm or more and 3.0 nm or less, and standard deviation of the Spk in a width direction of the surface of the magnetic layer is 0.5 nm or less.

A reference spiral is written on a recording surface of a magnetic storage disk that is free of position or timing information. The reference spirals are written on the recording surface with a substantially uniform slope by using open loop control of the position of a read/write head in conjunction with an iterative learning control scheme. A voltage profile applied to a voice coil motor is adapted over multiple iterations of moving the read/write head across the recording surface to closely approximate a target voltage profile, and the reference spiral is written using the adapted voltage profile. In addition, ramp contact detection based on actuator current profile may be employed to achieve full utilization of available actuator stroke.

Various illustrative aspects are directed to a data storage device comprising one or more disks, an actuator arm assembly comprising one or more disk heads and a voice coil motor (VCM), the VCM configured to operate in a PWM mode and a linear mode, and one or more processing devices configured to: seek the VCM towards a target track in the PWM mode; transition the VCM from the PWM mode to the linear mode, wherein the transitioning comprises switching an offset compensation value from a first offset compensation value to a second compensation offset value to compensate for a transition offset induced while transitioning the VCM from the PWM to the linear mode, wherein the first and the second offset compensation values correspond to the PWM and linear modes, respectively, and seek the VCM towards the target track in the linear mode for a linear mode time.

Implementations described and claimed herein includes a method comprising selecting a zone of one or more tracks on a disk drive having a plurality of magnetic sensors on a transducer head, determining a performance matrix related to the selected track zone, and selecting a first subset and a second subset of the plurality of magnetic sensors based on the determined performance matrix, wherein only the first subset of the plurality of magnetic sensors are used for data recovery in the selected track zone, and the second subset of the plurality of magnetic sensors are used for servo recovery.