Magnetic Disk Drive Adaptive Rewrite Parameter Control
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Solution Overview
Problem
As data recording density increases in hard disk drives (HDDs), the frequency of data rewrites necessary to prevent read hard errors due to magnetic interference between adjacent data tracks also increases, leading to performance degradation and data loss.
Innovation Solution
A magnetic disk drive system that calculates a rewrite parameter based on the degree of influence of data writes on adjacent tracks, using values defined by conditions such as temperature and radial position, and rewrites data when the parameter exceeds a threshold, rather than relying solely on the number of writes, to prevent data loss while maintaining performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If data recording density is increased, then storage capacity is improved, but magnetic interference between adjacent tracks increases causing data loss
Solution Approach 1:
The patent applies preliminary anti-action by proactively rewriting data in adjacent tracks before actual data loss occurs. The system monitors write counts and proactively rewrites adjacent tracks when the current track reaches a threshold write count, preventing magnetic interference from causing data loss rather than reacting after errors occur.
Solution Approach 2:
The patent changes parameters by dynamically adjusting rewrite thresholds based on track position, data density, and error rates. Different rewrite thresholds are set for different radial positions on the disk, allowing optimization of the balance between preventing data loss and minimizing performance impact for each specific track region.
2Reliability
If rewrite frequency is increased to prevent data loss, then data integrity is improved, but HDD performance deteriorates
Solution Approach 1:
The patent applies local quality by implementing selective rewriting based on track-specific parameters. Instead of uniformly rewriting all tracks at fixed intervals, the system adjusts rewrite frequency and thresholds according to each track's radial position, data density, and error characteristics, optimizing protection where needed while minimizing unnecessary rewrites elsewhere.
Solution Approach 2:
The patent uses partial action by rewriting only adjacent tracks when specific conditions are met, rather than rewriting all tracks continuously. The system performs selective rewriting based on write count thresholds, affecting only the minimum necessary tracks to prevent data loss while avoiding excessive rewriting that would degrade performance.
3Reliability
If rewrite thresholds are lowered to prevent data loss, then data integrity is improved, but number of rewrites increases causing performance degradation
Solution Approach 1:
The patent applies dynamics by making rewrite thresholds adaptive rather than static. The system dynamically adjusts rewrite thresholds based on operating conditions including track radial position, data density, temperature, and error rates, allowing optimization of the balance between data protection and performance for each specific operating context.
Solution Approach 2:
The patent uses feedback mechanisms by monitoring error rates, write counts, and track conditions to dynamically adjust rewrite thresholds. The system continuously gathers information about track health and interference levels, then uses this feedback to optimize rewrite timing and thresholds, preventing both premature and delayed rewrites.
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 frequency of unnecessary data rewrites, thereby preventing data loss in adjacent tracks and minimizing performance deterioration in HDDs, as demonstrated by reduced rewrite counts in comparison to conventional methods.
Implementation Method 1
a head element of a head slider supported by an oscillating actuator can write data to the data sectors
Implementation Method 2
read out data from the data sectors by accessing the desired data sector
Implementation Method 3
the leakage magnetic field from the head slider during a data write to the selected data track is known to affect the magnetic data in the adjacent tracks
Implementation Method 4
repeated magnetization changes in a data track are known to affect the magnetization of the adjacent data tracks
Data Source
AI summary
In one embodiment, a magnetic disk drive includes a magnetic disk having data tracks, a magnetic head, a motion mechanism for moving the magnetic head, and a controller. The controller adds a value to a rewrite parameter for a rewrite region based on a number of writes to data tracks related to the rewrite region, the value is chosen to reflect a degree of influence the number of writes have on the rewrite region, and the magnetic head rewrites data of the rewrite region when the rewrite parameter is greater than a threshold. In another embodiment, a method includes writing data tracks in a rewrite region, defining values reflecting a degree(s) of influence on the rewrite region, adding the values to a rewrite parameter upon writing data to the data tracks, determining that the rewrite parameter has reached or exceeded a threshold and rewriting data in the rewrite region.