Magnetic Disk Read Offset Correction for Shingled Tracks
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Solution Overview
Problem
Magnetic disk devices face challenges in efficiently recording and reading data due to the need for precise head positioning and large recording capacities to manage write and read processing errors across all tracks of the disk, particularly in shingled magnetic recording where tracks are written in a partially overlapping manner.
Innovation Solution
The magnetic disk device employs a system that calculates and records adjustment and correction read offset amounts based on write offset data, allowing the read head to adjust its position to optimize data retrieval by halving the sum of front and object write offset amounts, thereby improving read performance and reducing overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the path of the head at the time of write processing is recorded in a memory to improve error rate, then read performance is improved, but huge recording capacity is required to record paths of the head in all write processing corresponding to all tracks of the disk
Solution Approach 1:
The patent applies local quality by selectively recording correction read offset amounts only for specific sectors where write offset amounts exceed a threshold value, rather than recording data for all sectors uniformly. This localized approach reduces the overall recording capacity requirement while maintaining reliability improvement where it is most needed.
Solution Approach 2:
The patent implements partial action by recording correction data only for sectors that require it (those with write offset amounts greater than a threshold), rather than recording for all sectors. This partial recording approach reduces the burden on recording capacity while still improving read performance for the necessary sectors.
2Productivity
If correction read offset amounts are recorded for all sectors, then read performance is improved, but read processing overhead increases
Solution Approach 1:
The patent reduces read processing overhead by applying local quality - it only retrieves and applies correction read offset amounts for sectors where they exist (those where write offset exceeded the threshold), rather than processing all sectors uniformly. This selective approach minimizes the computational overhead while maintaining read performance benefits.
Solution Approach 2:
The patent implements partial action in the read processing stage by only performing correction lookups and applications for sectors that have correction data, rather than processing every sector. This reduces the average read processing overhead while maintaining improved read performance for the sectors that require correction.
3Reliability
If precise head positioning is maintained for all tracks, then data integrity is ensured, but the complexity of positioning control increases
Solution Approach 1:
The patent applies local quality to positioning control by only applying correction read offset amounts for sectors where the write offset exceeded a threshold value. This selective correction approach maintains data integrity for problematic sectors while reducing the overall complexity of positioning control compared to applying corrections uniformly across all sectors.
Data Source
AI summary
According to one embodiment, a magnetic disk device includes a disk including a first sector arranged at a first radial position deviated from a target position in a radial direction by a first offset amount larger than a first threshold value, a head that writes data to the disk and reads data from the disk, and a controller that reads the first sector by arranging the head at a second radial position deviated from the target position by a second offset amount different from the first offset amount.