Sector Mapout for Low Coercivity Media in Disk Drives
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Solution Overview
Problem
Magnetic disks in disk drives experience variations in coercivity due to the shadowing effect caused by sputtering claws during manufacturing, leading to issues like adjacent track interference, data degradation, and reduced storage capacity, as current techniques either reduce aerial density or provide limited mitigation against poor writes.
Innovation Solution
Mapping out sector IDs in sputter shadow areas, either every other track or every third track, to avoid writing or reading data from these regions, allowing for higher aerial density without significantly impacting storage capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If sputtering claws are used during manufacturing, then film deposition is achieved, but coercivity variations and adjacent track interference occur
Solution Approach 1:
The patent applies preliminary action by detecting sputter shadow areas and mapping out sector IDs before normal data writing operations begin. The controller identifies regions with abnormal coercivity during manufacturing and pre-marks these sectors as unavailable, preventing future data writing in these problematic areas. This advance preparation eliminates adjacent track interference issues before they affect data storage operations.
2Object-affected harmful factors
If aerial density is reduced to mitigate coercivity effects, then adjacent track interference decreases, but storage capacity is reduced
Solution Approach 1:
The patent applies local quality by selectively mapping out sector IDs only in specific sputter shadow areas rather than reducing aerial density across the entire disk surface. The controller identifies precise radial and angular regions affected by sputtering claws and marks only those localized sectors as unavailable. This allows the majority of the disk surface to maintain high aerial density while isolated problematic regions are excluded, preserving overall storage capacity.
3Object-affected harmful factors
If sector IDs are mapped out in sputter shadow areas, then adjacent track interference is reduced, but storage capacity is impacted
Solution Approach 1:
The patent applies partial action by mapping out sector IDs selectively in every other track or every third track within sputter shadow areas, rather than marking all sectors in these regions. The controller implements a pattern where only certain tracks receive the mapout treatment, allowing partial utilization of sputter shadow areas. This approach provides sufficient mitigation against adjacent track interference while maximizing the usable storage capacity within affected regions.
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 approach reduces adjacent track interference, minimizes data degradation, and enhances storage capacity by maintaining higher aerial density while mitigating the effects of coercivity variations, thus improving disk drive performance.
Implementation Method 1
these sputtering claws (also referred to as prongs) cause a shadowing effect on the magnetic disks
Implementation Method 2
During the manufacture of magnetic disks used in disk drives (also referred to as HDDs), the magnetic disks are physically supported by a plurality of sputtering claws during sputtering film deposition
Data Source
AI summary
Various illustrative aspects are directed to a data storage device comprising one or more disks, an actuator assembly comprising one or more disk heads; and one or more processing devices, configured to detect a plurality of areas with a coercivity lower than a threshold on the one or more disks; map out one or more sectors in each of the plurality of lower coercivity areas on the one or more disks; write data to, or read data from, the one or more disks, based at least in part on mapping out the one or more sectors in each of the plurality of lower coercivity areas. In some embodiments, the writing or reading data comprises writing data to, or reading data from, one or more sectors of the one or more disks that are not mapped out.