Magnetic Disk Head Overrun Control via Dynamic WOS Threshold
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Solution Overview
Problem
In magnetic disk apparatuses, overruns of the magnetic head during data writing can lead to data loss on adjacent tracks due to adjacent track interference, and existing methods to mitigate this, such as rewriting data, increase costs and processing time.
Innovation Solution
The magnetic disk apparatus adjusts the Write Off-Track Slice (WOS) threshold and vibration damping threshold dynamically based on overrun occurrences to prevent data loss without rewriting data on adjacent tracks, by tightening the WOS and increasing the damping threshold when overruns happen, thereby reducing the risk of data loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the magnetic head operates with standard WOS threshold during data writing, then writing speed and productivity are maintained, but data loss occurs on adjacent tracks due to overruns and adjacent track interference
Solution Approach 1:
The patent applies dynamics by making the WOS threshold adjustable rather than fixed. The controller dynamically changes the WOS threshold value based on detected overrun conditions, switching between a first threshold value (stricter) and a second threshold value (less strict). This dynamic adjustment allows the system to maintain higher reliability when overruns occur while preserving productivity during normal operation, resolving the contradiction between data integrity and writing speed.
Solution Approach 2:
The patent implements parameter changes by modifying the WOS threshold parameter in response to detected overruns. When an overrun is detected, the controller changes the WOS threshold from a standard value to a stricter first threshold value for subsequent writing operations on affected tracks. This parameter change prevents further data loss on adjacent tracks while allowing the system to return to normal operation once the condition is resolved, thus protecting data integrity without permanently reducing productivity.
2Reliability
If data rewriting is performed to prevent data loss from adjacent track interference, then data integrity is improved, but processing time and operational costs increase
Solution Approach 1:
The patent applies preliminary action by proactively adjusting the WOS threshold before data loss can occur on adjacent tracks. When an overrun is detected during writing to a first track, the controller preemptively changes the WOS threshold for subsequent operations on second tracks (adjacent tracks) to prevent potential data loss. This preliminary protective measure eliminates the need for time-consuming data rewriting operations, as the stricter threshold prevents the harmful effect before it manifests, thus protecting data integrity while avoiding additional processing time.
Solution Approach 2:
The patent implements feedback by continuously monitoring magnetic head position and detecting overruns, then using this information to adjust the WOS threshold in real-time. The controller receives feedback about overrun conditions and automatically modifies the writing parameters to prevent data loss on adjacent tracks. This closed-loop feedback mechanism replaces the open-loop approach of preventive data rewriting, achieving the same data protection goal without the time penalty of rewriting operations.
3Reliability
If the WOS threshold is made stricter to prevent overruns, then data loss risk is reduced, but magnetic head operation becomes more constrained and writing efficiency decreases
Solution Approach 1:
The patent applies dynamics by making the WOS threshold adjustable rather than fixed. The controller dynamically changes the WOS threshold value based on detected overrun conditions, switching between a first threshold value (stricter) and a second threshold value (less strict). This dynamic adjustment allows the system to maintain higher reliability when overruns occur while preserving productivity during normal operation, resolving the contradiction between data integrity and writing speed.
Solution Approach 2:
The patent implements parameter changes by modifying the WOS threshold parameter in response to detected overruns. When an overrun is detected, the controller changes the WOS threshold from a standard value to a stricter first threshold value for subsequent writing operations on affected tracks. This parameter change prevents further data loss on adjacent tracks while allowing the system to return to normal operation once the condition is resolved, thus protecting data integrity without permanently reducing productivity.
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 reduces the risk of data loss on adjacent tracks during data writing by controlling the magnetic head's operation, minimizing the impact of overruns without the need for data rewriting, thus enhancing data integrity and reducing operational costs and processing time.
Implementation Method 1
a magnetic head performs read/write from/to a plurality of tracks
Data Source
AI summary
According to one embodiment, a magnetic disk apparatus includes a magnetic disk, a magnetic head, and a controller. The magnetic disk includes a plurality of tracks. The magnetic head performs read/write from/to the plurality of tracks. The controller controls, in a first case in which, during execution of write to a first track among the plurality of tracks, a position of the magnetic head is displaced from a target position corresponding to the first track toward a second track, and a first distance exceeds a first threshold, write to the second track under a condition different from a condition in a second case in which the first distance is less than the first threshold. The second track is a track different from the first track among the plurality of tracks. The first distance is the distance between the target position and the position of the magnetic head.