Magnetic Disk Controller HFW Signal Standardization
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Solution Overview
Problem
Magnetic disk devices face challenges with high fly write (HFW) events, where the head lifts due to contamination, leading to insufficient magnetization and potential read errors, necessitating a lower bit per inch (BPI) setting, which results in reduced areal density capability and increased bit error rates due to varying signal strength across servo sectors.
Innovation Solution
A magnetic disk device with a controller that records signal strength data for each servo sector and standardizes the signal strength by subtracting signal strength record data from the target servo reproduction signal, allowing for accurate determination of HFW and enabling reliable write operations without the need for reduced BPI settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the BPI is set lower to avoid read errors from HFW, then reliability is improved, but areal density capability deteriorates
Solution Approach 1:
The system performs preliminary detection of HFW events by reading servo sectors and calculating signal strength variations before actual data writing. This allows the system to identify contaminated regions in advance and prevent writing data that would later cause read errors, thereby maintaining high BPI settings without sacrificing reliability
Solution Approach 2:
The system continuously monitors signal strength of servo sectors and uses this feedback to detect HFW events. By calculating the variation in signal strength across multiple servo sectors and comparing it against thresholds, the system can identify when the head is flying at an abnormally high altitude and take corrective actions such as rewriting affected sectors
2Productivity
If high TPI is used to increase areal density, then productivity is improved, but measurement precision deteriorates due to weakened reproduction signal amplitude
Solution Approach 1:
The system uses feedback from servo sector readings to detect HFW events. By continuously monitoring the signal strength of servo sectors and comparing variations across multiple sectors, the system can identify abnormal conditions even with high TPI where signal amplitudes are weakened. The feedback mechanism allows the system to distinguish between normal signal variations and actual HFW events
Solution Approach 2:
The system divides the disk surface into multiple servo sectors and evaluates signal strength independently for each sector. This segmentation allows the system to detect localized HFW events and distinguish them from global signal strength variations, thereby maintaining measurement precision even when using high TPI configurations
3Ease of operation
If threshold-based detection is used for HFW, then ease of operation is improved, but measurement precision deteriorates due to high-frequency variation and NRRO components
Solution Approach 1:
The system divides detection into multiple stages: first dividing the disk into servo sectors for individual signal strength evaluation, then grouping sectors for comparative analysis. This multi-level segmentation allows the system to filter out high-frequency variations and NRRO components by comparing across multiple spatial locations, thereby improving detection accuracy while maintaining operational simplicity
Solution Approach 2:
The system performs multiple readings of servo sectors and uses comparative analysis beyond a single threshold check. By evaluating signal strength across multiple sectors and using statistical comparison, the system achieves more precise HFW detection than simple threshold-based methods, while still maintaining ease of operation through automated processing
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
The solution effectively detects HFW events, preventing read errors and maintaining high areal density capability by ensuring consistent signal strength across servo sectors, thus improving data reliability and storage efficiency.
Implementation Method 1
the magnetization of the disk by the writing can become insufficient
Implementation Method 2
the amplitude of a reproduction signal when a predetermined region is read is weakened
Data Source
AI summary
According to one embodiment, a magnetic disk device includes a disk that has a track including a first servo sector and a second servo sector that is different from the first servo sector, a head that writes data to the disk and reads data from the disk, and a controller that records first signal strength record data related to a signal strength at which first target servo data that is a target of the first servo sector is read, and standardizes first signal strength data related to a signal strength at which the first target servo data is read when the first target servo data is read.