SSD Dynamic Ingress Throttle for Low Latency
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Solution Overview
Problem
Conventional SSD designs face bottlenecks due to the mismatch between the rate at which hosts submit write commands and the SSD's ability to process them, leading to increased write latency and inability to handle sudden bursts of commands effectively.
Innovation Solution
Implementing a dynamic ingress throttle rate for write commands based on the remaining capacity of the event queue and write data buffer, which can be adjusted over time or after a certain number of commands are executed, to prevent queue overflow and maintain optimal buffer levels, using a PID controller to calculate the throttle rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the SSD controller accepts write commands at a high rate to improve throughput, then I/O performance is improved, but write latency increases and the system becomes unable to handle sudden bursts of commands
Solution Approach 1:
The patent implements a dynamic ingress throttle rate that adjusts based on real-time monitoring of event queue and write data buffer status. The throttle rate transitions from a static fixed value to a dynamic parameter that adapts to changing system conditions, allowing the SSD to optimize between throughput and latency based on current queue fullness and processing capacity
Solution Approach 2:
The system continuously monitors the status of event queues and write data buffers, using this feedback to adjust the ingress throttle rate. When queues approach fullness or processing slows down, the throttle rate is reduced to prevent overflow and maintain low latency. This closed-loop feedback mechanism enables the system to respond to changing conditions and maintain optimal performance
2Quantity of substance
If the event queue and write data buffer are allowed to fill completely to maximize data storage capacity, then more commands can be processed, but write latency spikes and burst commands cannot be handled
Solution Approach 1:
The system performs preliminary actions by proactively throttling the ingress rate before the event queue or write data buffer becomes completely full. By monitoring queue status in advance and adjusting the throttle rate preemptively, the system prevents latency spikes and maintains the ability to handle burst commands, rather than waiting for queues to overflow
Solution Approach 2:
The patent changes the operational parameters of the SSD by dynamically adjusting the ingress throttle rate based on queue status. This parameter change allows the system to balance between maximizing data storage capacity in queues and maintaining reliable, consistent I/O performance by preventing queue overflow conditions
3Productivity
If a fixed high ingress rate is used to maximize throughput, then I/O performance is improved, but the system cannot adapt to varying processing speeds caused by garbage collection or wear leveling operations
Solution Approach 1:
The system replaces a static fixed ingress rate with a dynamic adaptive throttle rate that responds to changing processing conditions. When garbage collection or wear leveling operations reduce processing speed, the throttle rate automatically decreases to match the reduced capacity, preventing queue overflow. When processing speed increases, the throttle rate can increase accordingly, maximizing throughput
Solution Approach 2:
The system uses feedback from monitoring event queue status and write data buffer status to adjust the ingress throttle rate in real-time. This feedback mechanism enables the system to adapt to varying processing speeds caused by background operations like garbage collection and wear leveling, maintaining optimal throughput while preventing latency spikes during low-processing-periods
Data Source
AI summary
A method of managing writing data to a Solid State Drive (SSD). The method includes determining a remaining capacity of an event queue for queuing write commands for execution by the SSD. Dynamically setting an ingress throttle rate of write commands, transferred from a host interface to the event queue based on the remaining capacity of the event queue, during the operation of then SSD and transferring the write commands to the event queue at ingress throttle rate. The method also includes inputting write data associated with the write commands into a write data buffer.