Multi-Revolution HDD Servo Layout With Reduced Overhead Fields
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Solution Overview
Problem
Conventional hard disk drives face limitations in achieving high-density storage without compromising performance due to excessive servo overhead, which consumes valuable media space and increases manufacturing costs.
Innovation Solution
The method involves storing repeatable runout (RRO) correction information outside the servo pattern, such as in data sectors or off-disk media, and using multi-revolution operations to compensate for reduced servo fields, thereby optimizing areal density and storage capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional servo patterns with full overhead fields are used, then positioning accuracy and reliability are maintained, but storage density is reduced due to excessive servo overhead consuming media space
Solution Approach 1:
The patent extracts RRO correction information from the traditional servo pattern and stores it separately in data sectors or off-disk memory. This removes the burden from servo fields, allowing them to be minimized while maintaining positioning reliability through the separately stored correction data.
Solution Approach 2:
The patent moves RRO correction information from the two-dimensional servo pattern on the disk surface to a separate storage dimension (data sectors or off-disk memory), effectively adding a new dimension for storing correction data without consuming servo media space.
2Quantity of substance
If RRO correction information is stored outside the servo pattern, then storage density increases, but command completion time increases due to reduced servo overhead
Solution Approach 1:
The patent performs RRO correction calculations and prepares positioning data in advance during disk rotation, storing correction information in data sectors that are read during the rotation. This preliminary preparation allows the servo system to use minimal overhead fields while maintaining timely positioning through pre-computed correction data.
Solution Approach 2:
The patent maintains continuous positioning operations by storing RRO correction information in data sectors that are continuously available during disk rotation, ensuring that correction data can be retrieved without interrupting the continuous rotation and data operations.
3Manufacturing precision
If full servo overhead fields are written in every servo wedge, then positioning accuracy is maintained, but manufacturing complexity and test time increase
Solution Approach 1:
The patent applies different quality levels to different parts of the servo system: minimal servo overhead fields are written in each servo wedge for basic positioning, while comprehensive RRO correction information is stored separately in data sectors, allowing each component to have the appropriate level of detail for its function.
Solution Approach 2:
The patent segments the positioning information into two parts: basic servo fields in the servo wedges for immediate positioning needs, and detailed RRO correction information in data sectors for enhanced accuracy, allowing independent optimization of each segment.
Data Source
AI summary
Disclosed are hard disk drives (HDDs), and methods for use therewith, that utilize reduced overhead servo fields, thereby simplifying the servo system. Reduced overhead servo fields may be of particular use in HDDs that utilize multi-revolution storage techniques to store data at much higher densities than what is possible for conventional HDDs. The relaxed performance requirements of high-density, multi-revolution drives provides opportunities for reducing servo overhead, thereby potentially further increasing the areal density capability of the magnetic media. Servo overhead may also be reduced by placing certain servo data on flash or other memory off of the media disk rather than in the servo fields written to the media disk.