Track Pitch Capability Identification in Data Storage Devices
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Solution Overview
Problem
Current data storage devices face challenges in determining optimal track pitch due to limitations in separating servo-mechanical and recording subsystem effects, leading to poor understanding and non-optimum track density solutions, which increases susceptibility to track misregistration and errors.
Innovation Solution
A method is developed to determine a baseline track pitch by evaluating the recovery rate of data written to a target track with an adjacent aggressor track, independent of track misregistration, and combining this with compensation values for repeatable and non-repeatable runout components to set a final track pitch, thereby optimizing track density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If track pitch is reduced to increase track density, then storage capacity is improved, but susceptibility to track misregistration and errors increases
Solution Approach 1:
The patent segments the determination of track pitch capability into distinct components: repeatable runout (RRO) and non-repeatable runout (NRRO). By separately measuring and compensating for these effects, the system can accurately determine the baseline track pitch capability without contamination from misregistration effects, enabling safer reduction of track pitch while maintaining reliability.
Solution Approach 2:
The patent changes the parameter being measured from general track error rates to specific code word failure rates under controlled conditions. By varying the track pitch parameter systematically and measuring code word failures at each pitch, the system identifies the baseline track pitch capability where half the code words are undecodeable, providing an optimized pitch value that maximizes density while maintaining reliability.
2Device complexity
If indirect measurements of available parameters are used to establish track pitch, then measurement process is simplified, but understanding of system capabilities and optimality is poor
Solution Approach 1:
The patent extracts and isolates the baseline track pitch capability from confounding factors by taking measurements under controlled conditions where repeatable and non-repeatable runout effects are minimized or accounted for. This extraction of the pure track pitch capability metric provides precise understanding of system capabilities without the noise of indirect measurements.
Solution Approach 2:
The patent uses code word failure rate as an intermediary metric to indirectly measure track pitch capability. Instead of directly measuring complex servo-mechanical parameters, the system uses the easily measurable code word failure rate as a mediator that reflects the underlying track pitch capability, providing both simplicity and precision.
3Quantity of substance
If track pitch is optimized for maximum density, then storage capacity increases, but separation of servo-mechanical and recording subsystem effects becomes difficult
Solution Approach 1:
The patent performs preliminary measurements to establish the baseline track pitch capability before optimizing for maximum density. By first determining the RRO and NRRO components and calculating the baseline capability, the system creates a reference point that enables subsequent optimization while maintaining the ability to separate and understand individual subsystem contributions.
Data Source
AI summary
Method and apparatus for identifying the track pitch capability of a recording device, such as but not limited to a recording system and/or a servo control system in a data storage device. In accordance with some embodiments, data are written to first and second tracks at an initial track pitch such that the second track at least partially overlaps the first track. Data are arranged on the first track in code words each having a fixed plurality of bits which are decoded as a group by a data channel. The code words are transferred from the first track to the data channel, and a final track pitch for subsequent tracks is responsive to a distance at which nominally half of the code words are undecodeable by the data channel.