Runt Write Command Execution in Disk Drive Systems
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Solution Overview
Problem
Existing disk drive systems face inefficiencies in head positioning and data writing due to vibrations and settling delays, leading to incomplete write commands and increased latency, which affect performance and power consumption.
Innovation Solution
Implementing 'runt write commands' that are executed opportunistically as free commands within the command queue, allowing for partial execution of write commands during rotational latency or between access commands, and flushing pending commands to non-volatile memory when thresholds are reached to manage memory and optimize seek times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the system waits for complete write commands to execute before proceeding, then data integrity is maintained, but latency increases and throughput decreases
Solution Approach 1:
The patent segments write commands into complete commands and runt commands, allowing them to be processed independently. This segmentation enables the system to execute runnable runt commands without waiting for complete command batches, reducing latency while maintaining data integrity through proper bookkeeping of executed portions.
Solution Approach 2:
The patent performs preliminary analysis of command queues to identify runnable runt commands before executing main commands. By pre-identifying and separating executable runt commands, the system can execute them immediately without blocking, reducing overall latency while ensuring data integrity through tracking of command execution states.
2Productivity
If the system executes more aggressive seek profiles to reduce access time, then productivity improves, but head positioning accuracy deteriorates due to vibrations and settling delays
Solution Approach 1:
The patent dynamically adjusts seek profiles based on command queue analysis and head positioning requirements. By making seek profiles adaptive rather than static, the system can optimize for speed when appropriate and for accuracy when needed, resolving the contradiction between productivity and positioning precision.
Solution Approach 2:
The patent implements feedback mechanisms that monitor head positioning accuracy and command execution status, using this information to adjust subsequent seek operations. This feedback loop ensures that aggressive seeks are used only when positioning accuracy is sufficient, maintaining both high throughput and accurate positioning.
3Reliability
If the system buffers runt commands in memory until thresholds are reached, then data integrity is improved, but memory usage increases and power consumption rises
Solution Approach 1:
The patent applies partial buffering by maintaining runt command queues only when necessary and flushing them at optimized thresholds. This partial action approach balances data integrity requirements with power consumption constraints, avoiding continuous high-power buffering while ensuring data is not lost.
Solution Approach 2:
The patent implements threshold-based flushing of runt command buffers to non-volatile memory or execution, discarding the high-power buffering state when thresholds are reached. This allows the system to recover power by transitioning from active buffering to lower-power states while preserving data integrity through proper buffer management.
4Productivity
If the system executes runt commands inline with queued commands, then throughput improves, but command execution order complexity increases
Solution Approach 1:
The patent segments the command execution process into separate phases: identification of runnable runt commands, execution of those runt commands, and then execution of main queued commands. This segmentation simplifies the overall execution order by creating clear phases rather than complex interleaved scheduling.
Solution Approach 2:
The patent introduces an intermediary runt command queue and management logic that mediates between incoming commands and the main execution queue. This intermediary structure simplifies execution order complexity by providing a dedicated buffer and management mechanism for runt commands, isolating them from the main queue processing logic.
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 minimizes latency, reduces power consumption, and enhances throughput by allowing more aggressive seek profiles and reducing adjacent track interference, while ensuring data integrity and host performance visibility.
Implementation Method 1
a head connected to a distal end of an actuator arm which is rotated about a pivot by a voice coil motor (VCM)
Data Source
AI summary
A data storage device is disclosed comprising a head actuated over a disk comprising a plurality of data tracks. A plurality of access commands including a plurality of write commands are stored in a command queue, and the access commands are sorted into an execution order. A first write command is selected from the command queue based on the execution order, and a first part of the first write command is executed leaving a runt write command. The runt write command is executed between two of the sorted access commands so that the runt write command does not affect the execution order.