Magnetic Disk Control Apparatus Offtrack Error Correction
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Solution Overview
Problem
Conventional magnetic disk apparatuses fail to address write faults effectively, particularly in sectors where data writing has been completed, leading to potential read errors due to offtrack positions and environmental factors like jolts and atmospheric pressure variations.
Innovation Solution
A control apparatus that calculates the offtrack amount for the next servo frame and determines whether data needs to be rewritten in sectors before it, using a storage unit, calculating unit, and rewrite determining unit to assess and correct data writing errors even after the writing process is completed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If data writing is completed without post-writing determination, then writing speed is improved, but data accuracy deteriorates due to undetected offtrack write faults
Solution Approach 1:
The system performs preliminary determination of write faults by calculating the offtrack amount at the next servo frame position before the writing process is fully completed. This allows the system to identify potential offtrack write faults in advance and rewrite affected sectors, ensuring data accuracy without significantly compromising writing speed.
Solution Approach 2:
The system implements a feedback mechanism where the offtrack amount at the next servo frame is calculated based on previously stored offtrack amounts, and this information is used to determine whether rewriting is necessary. This feedback loop ensures that data writing accuracy is maintained by continuously monitoring and correcting potential offtrack conditions.
2Measurement precision
If the number of servo frames is increased to improve servo sampling precision, then offtrack detection accuracy is improved, but the number of sectors between servo frames decreases, requiring more frequent rewriting operations
Solution Approach 1:
The system performs rewriting operations only when necessary, based on the calculated offtrack amount at the next servo frame. Instead of rewriting all sectors between servo frames, the system selectively rewrites only those sectors where offtrack write faults are detected, thereby maintaining writing efficiency while ensuring data accuracy.
3Manufacturing precision
If rewriting is performed in all sectors between servo frames, then data accuracy is improved, but writing time is increased due to unnecessary rewriting operations
Solution Approach 1:
The system applies rewriting operations locally only to specific sectors where offtrack write faults are detected, rather than performing blanket rewriting across all sectors. This localized approach maintains data accuracy while minimizing the time loss associated with rewriting operations.
4Device complexity
If the maximum number of rewrite sectors is set to a fixed value, then device complexity is reduced, but adaptability to different track configurations deteriorates
Solution Approach 1:
The system dynamically determines the number of sectors to be rewritten based on the calculated offtrack amount at the next servo frame, rather than using a fixed maximum value. This dynamic approach allows the system to adapt to different track configurations and zone variations while maintaining manageable control complexity.
Data Source
AI summary
Offtrack amounts corresponding to every servo in which data writing has been completed is stored in a storage unit. Offtrack amount corresponding to a next servo frame, which is a servo frame present next to a servo frame for which data has been written, is calculated from the offtrack amounts stored in the storage unit. Based on the offtrack amount of the next servo frame, it is decided whether data needs to be rewritten in a sector present before the next servo frame.