Servo Write Timing Adjustment for Magnetic Disk Devices
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Solution Overview
Problem
In magnetic disk devices, maintaining equal intervals between servo sectors is challenging due to variations in track pitch, which affects data track alignment and recording density, leading to inefficiencies in servo control and data access performance.
Innovation Solution
The magnetic disk device adjusts write servo intervals and timings to match the intervals and access timings of servo sectors on an eccentric target route, ensuring equal access servo intervals and timings across one round of the target route, thereby improving servo control efficiency and data recording density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If servo sectors are written on a standard circular route, then the writing process is simple, but the intervals between servo sectors become unequal due to track pitch variations
Solution Approach 1:
The patent applies asymmetry by using an eccentric circular route instead of a standard concentric circular route for writing servo sectors. The eccentric route has its center offset from the disk center, which compensates for track pitch variations and achieves equal servo sector intervals despite the asymmetric writing path
Solution Approach 2:
The patent changes the writing route parameters by introducing eccentricity (offset distance from disk center) and adjusting the radius of the eccentric circle. By optimizing these parameters, the system achieves equal servo sector intervals while maintaining a relatively simple circular writing pattern
2Productivity
If track pitch variations are not compensated, then the servo control is simple, but data access performance deteriorates due to unequal servo sector intervals
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing the eccentric circular route parameters and servo sector timing information in a lookup table before actual data writing. This allows the servo control system to simply retrieve and execute pre-computed values, achieving equal servo sector intervals without complex real-time calculations
Solution Approach 2:
The patent introduces an intermediary lookup table that stores pre-computed eccentric route parameters and servo timing information. This intermediary structure mediates between the physical track pitch variations and the logical servo control, simplifying the control process while achieving equal servo sector intervals
Data Source
AI summary
According to one embodiment, a magnetic disk device including a disk, a head, and a controller configured to, when writing a first servo sector, a second servo sector, and a third servo sector in the order described according to a second route varying in a radial direction of the disk with respect to a first route, adjust first timing used to write the second servo sector next to the first servo sector, and adjust second timing used to write the third servo sector next to the second servo sector.