Magnetic Disk Drive Servo Preamble Length Adjustment
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Solution Overview
Problem
In magnetic disk drives, the fixed length of servo preamble data limits the optimization of servo frame length, which in turn restricts the increase in linear recording density, as it is set with a margin for worst-case phase acquisition independently of zones and heads.
Innovation Solution
The servo preamble length is adjustable for each zone, allowing it to be set to a value less than or equal to a reference length, enabling optimized phase acquisition and reducing the servo frame length, thereby increasing linear recording density by adjusting the number of repetitions of a repeated pattern in servo preamble data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the servo preamble length is set with a margin for worst-case phase acquisition, then phase acquisition reliability is improved, but the servo frame length cannot be reduced, limiting linear recording density
Solution Approach 1:
The patent applies local quality by setting different servo preamble lengths for different zones on the disk. Inner zones use longer servo preambles to ensure reliable phase acquisition due to higher linear velocities, while outer zones use shorter servo preambles since they operate at lower linear velocities and require less margin. This zone-specific optimization allows each region to have the minimum necessary preamble length, reducing overall servo frame length and increasing data capacity.
Solution Approach 2:
The patent implements dynamics by making the servo preamble length adjustable and variable rather than fixed. The system dynamically selects appropriate preamble lengths based on zone characteristics and head positioning requirements. This dynamic adjustment enables the servo frame structure to adapt to different operating conditions, optimizing both phase acquisition reliability and recording density across the entire disk surface.
2Productivity
If the servo frame length is reduced to increase data frame length, then linear recording density is improved, but phase acquisition reliability may be compromised
Solution Approach 1:
The patent applies parameter changes by systematically varying the servo preamble length parameter across different zones. By changing this critical parameter based on zone-specific requirements, the system achieves optimal balance between phase acquisition reliability and recording density. The controller adjusts the preamble length parameter to match the linear velocity characteristics of each zone, ensuring sufficient phase acquisition margin while maximizing data capacity.
3Device complexity
If a fixed servo preamble length is used for all zones, then device complexity is reduced, but data format efficiency cannot be optimized for each zone
Solution Approach 1:
The patent applies segmentation by dividing the disk into multiple zones, each with its own optimized servo preamble length. This segmentation allows the system to treat different radial regions independently, applying appropriate preamble lengths to each zone based on its specific requirements. The segmentation approach enables zoned optimization of data format efficiency while maintaining manageable system complexity through systematic zone-based control.
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 adjustment process enhances data format efficiency by allowing a reduction in servo preamble length, thereby increasing the bits-per-inch capacity of each zone, improving the overall data recording density without compromising phase synchronization.
Implementation Method 1
a head to read the servo frames from the disk via a read amplifier
Data Source
AI summary
According to one embodiment, a magnetic disk drive includes a disk and a controller. The disk includes a plurality of zones each having a plurality of tracks. The disk is formatted such that a plurality of servo frames are discretely recorded in each of the plurality of tracks. The plurality of servo frames include servo preamble data of a second length which corresponds to the zone having the track and which is less than or equal to a first length serving as a reference. The controller allows a head to read the servo frames from the disk via a read amplifier.