Magnetic Disk Servo Pattern Width Shifting for Sync Mark Detection
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Solution Overview
Problem
In magnetic disk devices, the narrow write width of the head leads to a reduced number of detected sync marks during the seek process, potentially causing sync mark detection failures and reducing the reliability of the self-servo write process due to fewer sync marks being detected compared to on-track readings.
Innovation Solution
The magnetic disk device writes an overwritten spiral servo pattern by shifting normal spiral servo patterns in the radial direction, increasing the width and enhancing sync mark detection during both on-track and seek processes, thereby improving reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the write width of the head is narrow, then the head can access more tracks, but the width of the spiral servo pattern becomes narrow and the number of detected sync marks during seek is reduced
Solution Approach 1:
The patent applies dimensional change by transitioning from a single-width servo pattern to a multi-width servo pattern. The servo pattern includes a first portion with a first width and a second portion with a second width that is wider than the first width. This multi-dimensional width structure allows the servo pattern to maintain sufficient sync mark density for reliable detection during seek operations while being written by a head with narrow write width, thus resolving the contradiction between head accessibility and detection reliability.
2Length of moving object
If the width of the spiral servo pattern is narrow, then the head write width can be small, but the number of detected sync marks during seek is reduced compared to on-track
Solution Approach 1:
The patent applies local quality by creating different width regions within the same servo pattern. The first portion of the servo pattern has a first width suitable for narrow write head, while the second portion has a second width that is wider to provide sufficient sync marks for reliable detection. This local differentiation of width ensures that each region serves its specific function optimally, resolving the contradiction between compact write width and reliable sync mark detection.
3Speed
If the number of sync marks detected during seek is small, then the seek process is faster, but the servo comes off and reliability of self-servo write is reduced
Solution Approach 1:
The patent resolves this contradiction by introducing a multi-width structure to the servo pattern. The wider second portion of the servo pattern provides a higher density of sync marks, ensuring reliable detection during seek operations even at high speeds. This dimensional change in the servo pattern structure allows the system to maintain both fast seek performance and high reliability by ensuring sufficient sync mark detection across the entire seek trajectory.
Data Source
AI summary
According to one embodiment, a magnetic disk device comprises a disk, a head that writes data to the disk and reads data from the disk, and a controller that controls a position of the head so as to write a first spiral servo pattern to the disk, and overwrite a second spiral servo pattern different from the first spiral servo pattern by shifting in a radial direction of the disk from the first spiral servo pattern.