Shingled Magnetic Recording Position Error Management
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Solution Overview
Problem
Shingled write magnetic recording (SMR) techniques face challenges in maintaining track pitch and reducing write retries due to positioning errors, which affect the recording capacity and efficiency of magnetic disk devices.
Innovation Solution
A magnetic disk device with a system controller that manages positioning errors by recording maximum positioning errors in nonvolatile memory and dynamically adjusting the drift-off level (DOL) to prevent write processing interruptions, allowing for resumed write operations with reduced retries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If shingled recording type magnetic disk device writes next recording track overlapping adjacent track to achieve high recording capacity, then recording capacity is improved, but track pitch control becomes more difficult and positioning errors increase
Solution Approach 1:
The system performs preliminary actions by recording maximum positioning errors in non-volatile memory during normal operations, and pre-calculating adjusted drift-off levels before power failures occur. This allows the system to resume write operations with corrected parameters after power restoration, preventing write retries and maintaining track pitch accuracy in shingled recording operations.
2Reliability
If magnetic disk device maintains strict track pitch control to reduce positioning errors, then write processing reliability is improved, but write processing speed decreases due to frequent interruptions and retries
Solution Approach 1:
The system implements feedback mechanisms by continuously monitoring positioning errors during write operations, recording maximum errors in non-volatile memory, and using this feedback to dynamically adjust drift-off levels. This closed-loop control maintains write processing reliability while minimizing interruptions, as the system proactively compensates for positioning errors rather than reacting to them after write failures occur.
Solution Approach 2:
The drift-off level is made dynamic rather than fixed, allowing the system to adjust the parameter based on recorded positioning errors. This dynamic adjustment optimizes write processing by adapting to actual track positioning conditions, maintaining reliability while improving speed through reduced write retries and interruptions.
3Productivity
If system records maximum positioning error in nonvolatile memory and adjusts drift-off level dynamically, then write processing performance is improved, but device complexity increases
Solution Approach 1:
The system performs self-service by automatically recording positioning errors, calculating adjusted drift-off levels, and managing write operation resumption without external intervention. The error management functions are integrated into the existing controller architecture, utilizing available non-volatile memory and control mechanisms, thereby improving write processing performance while minimizing the increase in device complexity through resourceful use of existing components.
Data Source
AI summary
According to one embodiment, a magnetic disk device includes a disk, a head that writes data to the disk and reads data from the disk, and a controller that overwrites a second track on a first track in a first track group, and records a maximum first positioning error in a first direction from the first track to the second track in the first track in a nonvolatile first recording area.