Magnetic Disk Drive Write Control with Dynamic Positioning Error Thresholds
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Solution Overview
Problem
In shingled write recording technology, positioning errors can lead to write inhibit determinations that result in data overwrite or destruction, requiring restarts and affecting storage capacity and recording density due to stringent threshold values for write inhibit decisions.
Innovation Solution
A magnetic disk drive system that includes a processor to detect current positioning errors, calculate predicted errors, and adjust threshold values dynamically based on error directions and magnitudes to prevent unnecessary write inhibits, thereby optimizing write operations and maintaining data integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If stringent threshold values are used for write inhibit determination, then data integrity is protected, but write operations are frequently inhibited causing reduced productivity
Solution Approach 1:
The patent applies dynamics by making the threshold value adjustable rather than fixed. The threshold for write inhibit determination is dynamically changed based on the positioning error direction: a first threshold is used when the error is in a first direction, and a second (higher) threshold is used when the error is in a second direction. This dynamic adjustment allows the system to maintain data integrity for critical write operations while permitting more operations to proceed when positioning errors are in less critical directions, thus resolving the contradiction between reliability and productivity.
Solution Approach 2:
The patent implements parameter changes by modifying the threshold value parameter based on the positioning error direction. Instead of using a single fixed threshold, the system changes the threshold parameter to different values (first threshold vs. second threshold) depending on the direction of the positioning error. This parameter change enables flexible control that protects data integrity when necessary while maintaining write operation productivity when positioning errors are within acceptable ranges in certain directions.
2Quantity of substance
If track pitch is narrowed to improve surface recording density, then storage capacity increases, but positioning errors more easily cause data overwrite
Solution Approach 1:
The patent applies local quality by making the threshold value different depending on the direction of the positioning error. When the positioning error is in the first direction (which would cause data overwrite in narrowed track pitch conditions), a stricter first threshold is applied. When the error is in the second direction, a more lenient second threshold is applied. This local differentiation in threshold quality allows the system to maintain high storage capacity through narrowed track pitch while providing targeted protection against data overwrite in the critical error direction.
3Device complexity
If write inhibit determination is delayed due to servo sector intervals, then processing complexity is reduced, but data corruption risk increases
Solution Approach 1:
The patent implements preliminary action by determining write inhibit status in advance based on the current positioning error direction before actually performing the write operation. By evaluating the positioning error direction and setting the appropriate threshold (first or second threshold) beforehand, the system prevents data corruption before it can occur, rather than detecting and responding to errors after they happen. This preliminary determination maintains reliability while keeping processing complexity manageable through straightforward directional comparison.
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 reduces the frequency of write inhibits, minimizes data corruption, and enhances storage capacity by allowing more flexible threshold settings, improving HDD performance and density without increasing the risk of data corruption.
Implementation Method 1
a magnetic head to write and to read data to and from the magnetic disk; and a processor that detects a current positioning error of the magnetic head on the magnetic disk
Data Source
AI summary
According to one embodiment, a magnetic disk drive includes a disk including a plurality of servo areas for detecting a positioning error, a head to write and to read data, and a processor. The processor detects a current positioning error of the head on the disk, while writing data to tracks of the disk so as to partially overlap with each other, calculates a predicted positioning error in a next servo area, determinates write inhibit, based on comparison between the current positioning error and a first threshold value, sets the first threshold value to a smaller value being used as the first threshold value to determinate the write inhibit in the next servo area.