Dual-Reader Servo Tracking for Multi-Sensor Hard Drives
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Solution Overview
Problem
Conventional servo writing processes on hard drives are time-consuming and inefficient, requiring multiple passes with multi-disk writers and occupying valuable space on the disk, while existing servo control systems struggle to accurately determine read/write head positions, limiting data storage capacity and throughput.
Innovation Solution
Implementing a dual-reader architecture for two-dimensional magnetic recording (TDMR) that reads servo marks during a single disk rotation, allowing for reduced servo writing frequency and improved format efficiency by determining tracking positions and cross-track displacements between multiple read heads using multiple servo marks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional servo writing processes use multiple passes with multi-disk writers, then servo marks can be written accurately, but the process becomes time-consuming and occupies valuable disk space
Solution Approach 1:
The patent divides the disk surface into distinct servo regions (inner servo region and outer servo region) with different servo writing frequencies. The inner servo region uses a first servo writing frequency while the outer servo region uses a second servo writing frequency, allowing each region to be optimized independently for both accuracy and time efficiency
Solution Approach 2:
Different servo writing frequencies are applied to different radial regions of the disk. The inner servo region receives more frequent servo marks (higher writing frequency) while the outer servo region receives less frequent servo marks (lower writing frequency), matching the local requirements of each region for positioning accuracy and storage efficiency
2Measurement precision
If servo writing frequency is increased to improve head positioning accuracy, then tracking precision improves, but data storage capacity is reduced
Solution Approach 1:
The patent applies different servo writing frequencies to different radial regions of the disk. The inner servo region uses a higher writing frequency for better positioning accuracy where precision is critical, while the outer servo region uses a lower writing frequency to maximize data storage capacity where less precision is required
Solution Approach 2:
The disk is segmented into inner and outer servo regions with different servo marking strategies. This segmentation allows the system to optimize the trade-off between positioning accuracy and storage capacity locally in each region rather than applying a uniform approach across the entire disk
3Productivity
If multiple readers are used for two-dimensional magnetic recording, then throughput and areal density increase, but determining accurate tracking positions becomes more difficult
Solution Approach 1:
The patent introduces position reference marks as intermediary reference points that facilitate accurate tracking position determination for multiple readers. These reference marks serve as common reference points that all readers can use to synchronize and determine their positions relative to each other and to the data tracks
Solution Approach 2:
Position reference marks are written in advance during the servo formatting process, before data writing begins. This preliminary action establishes a known reference framework that enables multiple readers to accurately determine their tracking positions during normal operation without requiring complex real-time calculations
Data Source
AI summary
At least a portion of a first servo mark is read using a first read head during a rotation of a disk, the rotation comprising no more than 360 degrees. At least a portion of a second servo mark is read using a second read head during the rotation of the disk. Tracking positions of the first read head and the second read head are determined during the rotation based on reading the first servo mark and the second servo mark.