Patterned Media Servo Zones with Overlap Regions
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Solution Overview
Problem
Existing servo writing technologies face challenges in writing servo data across servo zone boundaries on patterned magnetic disks, particularly in maintaining uniformity and compatibility with planarization constraints, which affects the alignment and accuracy of slider positioning over the disk.
Innovation Solution
The implementation of a zoned servo architecture with alternating series of concentric servo zones and overlap zones, where overlap zones are dual frequency zones or bootstrap zones, allowing for robust servo writing by accommodating varying servo frequencies and complying with planarization constraints through radial overlap lengths and extended sync patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If self-servo writing is used to write servo data from inner diameter to outer diameter, then servo data can be propagated step-wise, but the radial read-write offset (RWO) between read head and write head changes with slider angular position, causing writing inaccuracies across different radial zones
Solution Approach 1:
The magnetic disk surface is divided into multiple servo zones with different servo frequencies, where each zone has a constant servo frequency. This segmentation allows the system to accommodate the changing RWO by adjusting the servo frequency in different radial zones, thereby maintaining writing accuracy while preserving the efficiency of self-servo writing propagation.
Solution Approach 2:
Different servo frequencies are assigned to different radial zones of the magnetic disk. This local quality approach ensures that each zone is optimized for its specific radial position, compensating for the varying RWO effects at different angular positions and maintaining consistent servo writing accuracy across the entire disk surface.
2Adaptability or versatility
If constant servo frequency is used across the entire magnetic disk, then servo sector circumferential length increases proportionally with radial location, but this causes non-uniform pattern spacing that conflicts with planarization constraints on patterned media
Solution Approach 1:
The disk surface is segmented into multiple servo zones, each with a constant but different servo frequency. This allows the pattern spacing to be adjusted in each zone to maintain uniformity, satisfying planarization constraints while still providing adaptability through the zoned frequency structure.
Solution Approach 2:
The servo frequency parameter is changed across different radial zones rather than remaining constant. This parameter change allows the circumferential pattern spacing to be normalized across zones, ensuring uniform pattern appearance that complies with planarization constraints while maintaining system adaptability.
3Manufacturing precision
If servo zones are created with different servo frequencies to normalize circumferential length, then pattern uniformity is improved, but writing servo data across zone boundaries becomes more complex due to frequency transitions
Solution Approach 1:
Overlap zones are created at the boundaries between servo zones, where patterns from both adjacent zones are written in advance. This preliminary action ensures that when the read head encounters a zone boundary, the necessary patterns from both zones are already present, simplifying the writing process and reducing complexity while maintaining pattern uniformity.
Solution Approach 2:
Overlap zones serve as intermediary regions between servo zones of different frequencies. These zones contain patterns from both adjacent zones, acting as a buffer that facilitates smooth transitions and simplifies the writing process across zone boundaries without compromising the uniformity of the final pattern structure.
4Reliability
If overlap zones with dual frequency patterns are implemented, then servo writing robustness is improved by accommodating RWO variations, but the radial space required for overlap zones reduces the available data storage capacity
Solution Approach 1:
Overlap zones are implemented with a radial extent that is carefully controlled to provide just enough redundancy for robust servo writing. The overlap radial length is optimized to accommodate maximum RWO variations while minimizing the space consumed, thus balancing reliability improvement with data capacity preservation.
Data Source
AI summary
Embodiments described herein provide for patterned media concentric zones with an alternating series of concentric servo zones and overlap zones. The overlap zones facilitate the writing of servo data between servo zones of different servo frequency. The overlap zones may be dual frequency zones. The dual frequency zones have a first set of overlap patterns with the substantially identical pattern as the bordering lower frequency servo zone and a second set of overlap patterns with the substantially identical pattern as the bordering higher frequency servo zone. A bootstrap zone can be included near the inner diameter to assist initial servo writing. Alternatively the overlap zones are bootstrap zones. Such bootstrap zones have both bootstrap patterns and overlap patterns, the overlap patterns have the substantially identical pattern as a bordering servo zone. Bootstrap patterns only require DC magnetization for servo operability.