Magnetic Disk Testing Method for Write Spread Estimation
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Solution Overview
Problem
Current methods for testing magnetic disk devices are inefficient in accurately estimating signal quality degradation due to write spread, leading to prolonged test times and inaccuracies when estimating the number of write times required to prevent data overwrite.
Innovation Solution
A testing method and device that measure signal quality by obtaining index values from multiple positions on adjacent tracks to a target track, determining representative values, and estimating signal quality degradation for higher write times using these values, thereby reducing test time and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If data is repeatedly written onto the target track the guaranteed number of write times to accurately measure signal quality degradation, then measurement precision is improved, but loss of time increases significantly
Solution Approach 1:
The patent applies partial action by writing data only a fraction (1/10 or 1/100) of the guaranteed number of write times and then estimating the degradation corresponding to the full guaranteed number of write times from the measured degradation. This partial testing approach significantly reduces test time while still providing predictive information about long-term reliability
Solution Approach 2:
The patent creates a scaled-down model of the actual testing scenario by performing writes at reduced counts and using estimation algorithms to copy/predict the results that would be obtained from full guaranteed write time testing, thereby avoiding the need to perform the complete time-consuming actual test
2Loss of time
If data is written onto the target track only a fraction of the guaranteed number of write times to shorten test time, then loss of time is reduced, but measurement precision deteriorates due to large difference between estimated and actual degradation
Solution Approach 1:
The patent segments the adjacent track into multiple positions along the track width direction and obtains index values at each position. By determining a representative value from multiple segmented measurements rather than a single point measurement, the patent improves the accuracy of the estimation while still using reduced write counts
Solution Approach 2:
The patent changes the measurement approach by obtaining index values at multiple positions scattered in the width direction of the adjacent track and determining a representative value. This parameter change in the measurement methodology improves estimation accuracy without requiring proportional increases in write time
3Manufacturing precision
If the distance between the recording/reproducing head and the magnetic disk is narrowed to increase recording density, then manufacturing precision is improved, but object-affected harmful factors increase due to write spread causing side erase
Solution Approach 1:
The patent performs preliminary testing to determine the guaranteed number of write times before actual product deployment. By conducting these tests in advance and establishing write time guarantees, the patent enables manufacturers to confidently narrow the head-disk distance for higher recording density while having pre-validated that write spread remains controlled within acceptable limits
Solution Approach 2:
The patent uses feedback from measurement of signal quality degradation in adjacent tracks to determine the guaranteed number of write times. This feedback mechanism allows the system to establish safe write time limits that prevent harmful side erase effects, enabling tighter head-disk spacing while maintaining data integrity
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 allows for accurate estimation of signal quality degradation with reduced test time, enabling precise determination of write times to prevent data overwrite, and improving the write performance of magnetic heads.
Implementation Method 1
a recording/reproducing head that floats above a rotating magnetic disk records data onto the magnetic disk
Implementation Method 2
a recording/reproducing head that floats above a rotating magnetic disk records data onto the magnetic disk and reads data from the magnetic disk
Implementation Method 3
there is a higher possibility that the data recorded in the tracks adjacent to a predetermined target track is overwritten due to the magnetic field generated when data is written onto the target track. This is also called 'write spread'
Data Source
AI summary
A magnetic disk device testing method includes obtaining index values indicating the signal quality of an adjacent track at different positions scattered in the width direction in the adjacent track located in the vicinity of a target track on a magnetic disk after repeatedly writing data onto the target track, and determining a representative value of the index values indicating the signal quality of the adjacent track based on the obtained results, while incrementing the number of data write times; and estimating an index value indicating the signal quality of the adjacent track to be obtained where data is written onto the target track a larger number of times than the total number of data write times the data has been actually written in obtaining the index values, the index value being estimated with the use of the representative values decided in the representative value deciding.