Magnetic Disk Head Positioning Correction for Offtrack Data Integrity
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Solution Overview
Problem
Magnetic disk devices face challenges in maintaining data integrity due to positioning errors, which can lead to data erasure on adjacent tracks, and existing solutions degrade write performance by stopping operations when offtrack errors exceed threshold values.
Innovation Solution
A magnetic disk device and method that utilize an offtrack write table to correct positioning target positions based on errors from adjacent sectors, dynamically adjusting the positioning target to prevent data loss while maintaining write performance by using a correction amount calculated from positioning errors of sectors two tracks away.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If write operation is stopped when offtrack amount is large, then data erasure risk is reduced, but write performance is degraded
Solution Approach 1:
The system performs preliminary positioning error measurement and correction calculations before the actual write operation. By pre-calculating the corrected target position based on measured positioning errors, the system prepares compensation values in advance, allowing continuous write operations without stopping to maintain both data integrity and write performance
Solution Approach 2:
The system implements a feedback mechanism where positioning errors are measured, correction values are calculated, and the corrected target position is used for subsequent writes. This closed-loop feedback allows the system to dynamically adjust positioning based on actual error measurements, maintaining data integrity while enabling continuous operation
2Reliability
If positioning control is performed to reduce offtrack amount, then data erasure risk is reduced, but positioning precision requirements increase system complexity
Solution Approach 1:
The system introduces an intermediary correction value that mediates between the original target position and the actual head position. By calculating and applying a correction amount based on measured positioning errors, the system simplifies the control mechanism while achieving accurate positioning and data protection without complex real-time control algorithms
3Productivity
If write operation continues with small offtrack amount, then write performance is maintained, but risk of data erasure on adjacent tracks increases
Solution Approach 1:
The system dynamically changes the target position parameter based on measured positioning errors. By adjusting the corrected target position using correction values derived from actual positioning error measurements, the system compensates for offtrack conditions, allowing continuous writes while preventing data erasure on adjacent tracks
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 protects data on adjacent tracks by dynamically adjusting the positioning target, preventing degradation in write performance and reducing the frequency of write operation stops due to offtrack errors, thus ensuring data integrity and maintaining high write performance.
Implementation Method 1
a magnetic head positioned in a track provided at a predetermined track pitch of a magnetic disk, writing data to the track
Implementation Method 2
a magnetic head positioned in a track provided at a predetermined track pitch of a magnetic disk, writing data to the track, and reading data from the track
Data Source
AI summary
According to one embodiment, a magnetic disk device includes a magnetic disk, a magnetic head, and a controller including an offtrack write table, positioning the magnetic head, and registering an address at which data in a track is written and a positioning error of the magnetic head at the address for the track, in the offtrack write table. When writing data to a first sector, the controller corrects a positioning target position of the first sector, based on a positioning error of a second sector located on two tracks away in a radial direction from the first sector.