SMR Disk Controller Adaptive Track Center Positioning
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Solution Overview
Problem
Magnetic disk devices using shingled write magnetic recording (SMR) face challenges in accurately positioning heads for both writing and reading data due to overlapping tracks, which affects data integrity and processing efficiency.
Innovation Solution
The magnetic disk device incorporates a controller that acquires and records write position information for each track in a band region, allowing for adaptive track center control (ATC) during writing and read ATC control during reading, ensuring precise head positioning and improving data processing performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If shingled write magnetic recording is used to increase recording capacity, then the recording capacity is improved, but the head positioning accuracy deteriorates due to overlapping tracks
Solution Approach 1:
The patent applies preliminary action by pre-acquiring and storing write position information from adjacent tracks before performing read ATC control. The controller stores the central position and width information of previously written tracks in memory, then uses this stored information to calculate and adjust the head positioning during subsequent read operations, enabling accurate head positioning in SMR environments without real-time measurement interference.
Solution Approach 2:
The patent implements feedback through the read ATC (Read Adaptive Track Center) control mechanism. The controller continuously acquires actual head position information during read operations, compares it with the target position calculated from stored write position information, and adjusts the head positioning based on the position deviation. This closed-loop feedback system compensates for positioning errors caused by track overlapping in SMR.
2Measurement precision
If adaptive track center control is implemented to improve head positioning accuracy, then the positioning accuracy is improved, but the device complexity increases
Solution Approach 1:
The patent applies self-service by enabling the system to automatically acquire, store, and utilize its own write position information for subsequent read operations. The controller uses the information it previously generated during write operations to perform read ATC control, eliminating the need for external calibration or additional hardware components. The system serves itself by reusing internally generated data for positioning correction.
Solution Approach 2:
The patent implements universality by using the same controller unit to perform both write operations and read ATC control functions. The controller universally handles different operational modes (write and read) using a unified position information management mechanism, avoiding the need for separate dedicated systems for each function and thereby reducing overall device complexity.
3Productivity
If position information is acquired and stored for each track in band region, then the data processing efficiency is improved, but the memory requirements increase
Solution Approach 1:
The patent applies taking out by extracting only the essential position information (central position and width) from complete track data and storing only these critical parameters in memory. Rather than storing entire track datasets, the system extracts and retains only the minimum necessary information for read ATC control, reducing memory requirements while maintaining data processing efficiency.
Data Source
AI summary
According to one embodiment, a magnetic disk device includes a disk, a head configured to write data to the disk and read data from the disk, and a controller configured to write position information of the head when writing a first track of the disk and a second track partially overlapping with the first track in a first region of the first track at which read processing on the first track is started.