HAMR Disk Drive Command Selection to Minimize Laser Pre-Heating
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Solution Overview
Problem
Heat-assisted magnetic recording (HAMR) disk drives face challenges in minimizing mode hop, which occurs due to temperature changes in the laser diode, leading to unpredictable changes in write width and data integrity issues.
Innovation Solution
Implementing a next command selection algorithm that adds a penalty to commands requiring pre-heating or transitioning away from a pre-heated state, thereby minimizing pre-heat performance loss and reducing the occurrence of mode hop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pre-heating operations are performed frequently to avoid mode hop, then data integrity is improved, but productivity deteriorates due to increased cool down times
Solution Approach 1:
The system performs preliminary heating of the laser diode before write operations to ensure the laser is at the optimal temperature for writing, thereby avoiding mode hop and ensuring data integrity. This preliminary action is taken proactively rather than reactively, allowing the system to maintain reliability while minimizing the frequency of necessary pre-heating operations.
Solution Approach 2:
The system continuously monitors the temperature of the laser diode and uses this feedback to determine when pre-heating is necessary. By implementing a feedback mechanism that tracks temperature changes and laser diode state, the system can intelligently decide when to perform pre-heating operations, avoiding unnecessary cool down cycles while ensuring data integrity is maintained.
2Reliability
If the laser diode temperature is frequently adjusted, then mode hop is reduced, but the complexity of temperature control increases
Solution Approach 1:
The laser diode is designed to be self-regulating through its inherent thermal characteristics. The system leverages the natural cooling and heating properties of the laser diode material, allowing it to return to its optimal operating temperature automatically after write operations without requiring complex active cooling mechanisms. This self-service approach simplifies temperature control while maintaining reliable mode hop prevention.
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 minimizes the frequency of pre-heating operations, reducing cool down times and maintaining the laser diode at a constant temperature, thus minimizing mode hop and enhancing data integrity.
Implementation Method 1
a laser diode 352 via the waveguide and the NFT to project a plasmon onto disk surface 317 to heat an area of disk surface 317
Implementation Method 2
project a plasmon onto disk surface 317 to heat an area of disk surface 317
Implementation Method 3
The self-heating effect may cause a thermal expansion of one or more components of the head toward the disk surface
Implementation Method 4
The self-heating effect may cause a thermal expansion of one or more components of the head toward the disk surface, which results in a fly height transient
Data Source
AI summary
Various illustrative aspects are directed to a data storage device, method, and one or more processing devices that are configured to: estimate access times of a plurality of access commands included in a command queue of a disk drive containing the one or more disks; adjust a respective one of the access times of a respective one of the access commands based on the respective one of the access commands satisfying one of one or more conditions that indicate an increased likelihood of performing a pre-heating operation to heat a laser diode associated with a head of the disk drive; and select one of the access commands as a next command for execution in the disk drive based on the access times.