Magnetic Disk Write Processing with Dynamic Drift-Off Level Control
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Solution Overview
Problem
Magnetic disk devices face limitations in error correction due to the limited number of sectors that can be corrected using parity data, leading to inefficiencies in data recovery and write processing.
Innovation Solution
The magnetic disk device employs a dynamic drift-off level (DDOL) function, where priority numbers are set for sectors based on positioning errors, allowing for selective error correction and continued write processing even when positioning errors exceed certain thresholds, thereby reducing retry operations and improving write performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If error correction is executed for all sectors with positioning errors, then data recovery reliability is improved, but write processing time increases and productivity decreases
Solution Approach 1:
The patent applies local quality by differentiating error correction strategies based on sector characteristics. Sectors with small positioning errors (within a threshold) are prioritized for error correction using parity data, while sectors with large positioning errors are handled differently. This selective approach ensures that sectors most likely to benefit from error correction receive attention, improving overall data recovery reliability without uniformly processing all sectors and thus maintaining write processing speed.
Solution Approach 2:
The patent segments the track into different regions based on positioning error characteristics. By dividing the track into sectors with small positioning errors and sectors with large positioning errors, the system can apply different error correction strategies to each segment. This segmentation allows efficient use of limited parity data on sectors where it is most effective, while avoiding wasted correction attempts on sectors where positioning errors are too large to be corrected, thereby balancing reliability and productivity.
2Manufacturing precision
If retry operations are performed for sectors exceeding positioning error thresholds, then data accuracy is improved, but write processing efficiency deteriorates
Solution Approach 1:
The patent changes the parameter of positioning error threshold dynamically. Instead of using a fixed threshold for all sectors, the system determines thresholds based on actual positioning error measurements. Sectors with positioning errors below the threshold are subject to retry operations for improved data accuracy, while sectors exceeding the threshold are handled differently. This parameter change allows the system to adapt to varying positioning conditions, maintaining data accuracy where feasible while avoiding unnecessary retries that would reduce write processing efficiency.
3Reliability
If the number of sectors for error correction is increased, then data recovery capability is improved, but the complexity of error correction processing increases
Solution Approach 1:
The patent applies partial action by selecting only a specific number and type of sectors for error correction rather than attempting to correct all sectors. The system prioritizes sectors with small positioning errors that are most likely to be successfully corrected using parity data. This selective partial correction approach improves data recovery capability for the most critical sectors while avoiding the complexity and resource exhaustion that would result from attempting to correct all sectors, including those with large positioning errors where correction is unlikely to succeed.
Data Source
AI summary
According to one embodiment, a magnetic disk device includes a disk including a first track including a first sector, a second sector, and a first parity sector, a head, and a controller configured to, when writing a second track adjacent to the first track in the first direction, even if, in a third sector of the second track adjacent to the first sector in the first direction, a first upper limit in a second direction opposite to the first direction, continue the processing of writing data to the third sector, and if, in a fourth sector adjacent to the second sector in the first direction, a second upper limit in the second direction, stop the processing of writing data to the fourth sector.