Magnetic Disk Controller Offtrack Retry Logic
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Solution Overview
Problem
In high-capacity hard disk drives, track pitch abnormalities lead to adjacent track interference and close writing issues, as existing measures fail to account for varying track pitches, resulting in premature deterioration of track quality and data loss.
Innovation Solution
A magnetic disk device with a controller that detects offtrack amounts and executes specific retry processes based on slice values categorizing offtrack levels as slight, moderate, or severe, and adjusts the count operation for track groups to prevent rapid quality deterioration by performing refresh operations sooner for severe offtrack conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a constant track pitch is used for writing, then the manufacturing process is simple, but track pitch abnormality occurs causing adjacent track interference
Solution Approach 1:
The patent applies dynamics by transitioning from a static constant track pitch to a dynamic variable track pitch system. The writing process now adapts to actual track conditions by detecting offtrack amounts and adjusting subsequent writing positions, allowing the system to respond to pitch abnormalities while maintaining overall manufacturing simplicity through automated compensation mechanisms.
Solution Approach 2:
The patent implements feedback by continuously monitoring offtrack amounts during writing operations and using this information to adjust subsequent writing positions. The system detects track pitch abnormalities in real-time and feeds this information back to modify the writing process, preventing adjacent track interference while maintaining manufacturing efficiency through automated correction.
2Productivity
If track pitch abnormality is not considered, then the writing process is fast, but adjacent track interference occurs causing data loss
Solution Approach 1:
The patent applies preliminary action by performing detection and classification of offtrack amounts before executing the writing operation. The system categorizes pitch abnormalities into slight, moderate, or severe levels in advance, allowing it to pre-determine the appropriate response strategy and execute writing operations with predetermined adjustments, thus maintaining high writing speed while preventing data loss.
Solution Approach 2:
The patent implements parameter changes by dynamically adjusting writing parameters based on detected offtrack amounts. The system modifies writing position offsets, retry counts, and verification strategies according to the severity category, allowing fast writing operations under normal conditions while automatically applying protective measures when pitch abnormalities are detected, thus preventing data loss without sacrificing productivity.
3Device complexity
If uniform retry process is applied to all tracks, then the control logic is simple, but severe pitch abnormalities cannot be adequately handled
Solution Approach 1:
The patent applies segmentation by dividing the retry process into distinct stages based on offtrack severity: slight, moderate, and severe categories. Each category receives a tailored retry strategy with appropriate verification and position adjustment parameters. This segmented approach maintains relatively simple control logic through clear classification rules while effectively handling severe pitch abnormalities with specialized recovery procedures.
Solution Approach 2:
The patent implements dynamics by making the retry process adaptive rather than static. The system dynamically selects retry parameters based on real-time offtrack detection results, adjusting verification requirements, position offsets, and retry counts according to the severity category. This dynamic approach enhances track quality recovery for severe abnormalities while keeping control logic manageable through automated decision-making based on predefined thresholds.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively prevents rapid track quality deterioration due to pitch abnormalities, ensuring data integrity by executing appropriate recovery processes based on the severity of offtrack conditions and maintaining data quality over time.
Implementation Method 1
a magnetic head, a magnetic disk corresponding to the magnetic head, and a controller configured to write data to the magnetic disk with the magnetic head
Data Source
AI summary
According to one embodiment, any of a first process to perform a write retry to a write target track, a second process to perform the write retry and perform reading for data verification to an adjacent track, and a third process to perform the write retry and write data of the adjacent track to another track is executed based on a result of comparison between an offtrack amount and a plurality of different slice values.