SMR Magnetic Disk Controller Track Shifting
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Solution Overview
Problem
In magnetic disk apparatuses using shingled magnetic recording (SMR), the narrow track pitch makes it susceptible to adjacent track erasure (ATE), requiring collective updates of data across multiple tracks, which can be inefficient and affect read performance.
Innovation Solution
The magnetic disk apparatus employs a controller that reads data from multiple first tracks using SMR, updates the data by shifting the position of tracks from a fourth track to a third track by a first amount in the direction towards the end of the band area, and writes the updated data to offset positions, thereby reducing the impact of ATE and improving write performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If shingled magnetic recording (SMR) is used to narrow track pitch, then recording density is improved, but susceptibility to adjacent track erasure (ATE) increases
Solution Approach 1:
The patent divides the magnetic disk into multiple band areas, each containing multiple tracks. By organizing tracks into bands and implementing collective updates within each band, the system manages ATE susceptibility at a localized level while maintaining high recording density through SMR. This segmentation allows independent management of different track regions, reducing the propagation of ATE effects across the entire disk.
Solution Approach 2:
The patent implements preliminary actions by performing collective updates of multiple tracks before data writes when ATE is detected. The controller proactively identifies tracks susceptible to ATE and pre-performs read-modify-write operations on entire bands, ensuring data integrity before potential erasure issues occur. This preliminary action prevents data corruption by addressing ATE susceptibility before it affects stored information.
2Reliability
If collective updates of multiple tracks are performed to address ATE, then data integrity is improved, but update time increases
Solution Approach 1:
The patent applies partial action by performing collective updates only on specific bands containing tracks susceptible to ATE, rather than updating the entire disk. The controller identifies affected bands and limits update operations to those specific regions, reducing overall update time while maintaining data integrity for vulnerable tracks. This selective approach balances reliability improvement with time efficiency.
Solution Approach 2:
The patent changes operational parameters by dynamically adjusting update strategies based on detected ATE conditions. When ATE is detected in certain bands, the system activates collective update mode for those bands; when no ATE is detected, normal write operations continue without collective updates. This parameter change allows the system to optimize between data integrity and update speed based on actual disk conditions.
3Object-affected harmful factors
If track positions are shifted to offset positions, then ATE influence is reduced, but read performance may deteriorate due to retry operations
Solution Approach 1:
The patent applies preliminary anti-action by preemptively shifting track positions to offset positions before data writes when ATE susceptibility is detected. This pre-shift prevents ATE from affecting the original track positions, countering the harmful effect before it occurs. The offset positioning creates a protective buffer that reduces ATE influence on critical data tracks.
Solution Approach 2:
The patent implements feedback mechanisms by monitoring read operations for signs of ATE and dynamically adjusting track positioning strategies. When retry operations indicate potential ATE issues, the system responds by shifting track positions to offset locations. This feedback loop allows the system to adapt to actual ATE conditions and optimize the balance between ATE protection and read performance based on real-time disk health information.
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 the time required for data updates and improves write performance by minimizing the influence of ATE and suppressing read performance deterioration due to retry operations.
Implementation Method 1
a magnetic head that writes data to be written on the magnetic disk to multiple first tracks
Implementation Method 2
a magnetic head that reads data stored on the magnetic disk from the multiple first tracks
Data Source
AI summary
According to an embodiment, a controller of a magnetic disk apparatus reads band data from a band area where multiple first tracks are provided. The controller updates the read band data with write data received from a host. When an update portion of the updated band data is not included in data for a head track of the band area, the controller writes, to offset positions, pieces of the updated band data for specified tracks from a track serving as a write destination to an end track. The offset positions are obtained by shifting a position of each of the specified tracks by a predetermined amount in a direction to an end of the band area.