Storage Controller Threshold History Buffer for Read Latency
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Solution Overview
Problem
Flash storage devices experience increased read latency due to the need to send a set features command prior to each dynamic read operation, which can result in inefficiencies when multiple commands with identical read voltage threshold offsets are sent, impacting performance.
Innovation Solution
Implementing a threshold history buffer and comparator within the storage device to identify and store the last read voltage threshold vector for each die or page, allowing the controller to refrain from sending duplicate set features commands when the threshold offset has not changed, thereby optimizing read operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a set features command is sent before each dynamic read to modify read voltage thresholds, then data identification accuracy is improved, but read latency increases
Solution Approach 1:
The patent applies preliminary action by pre-modifying the read voltage threshold using a set features command before the dynamic read operation. This ensures the threshold is already optimized when the read occurs, improving data identification accuracy without adding latency during the actual read process.
Solution Approach 2:
The patent implements dynamics by making the read voltage threshold modifiable and adjustable based on actual read conditions. The threshold is dynamically modified using set features commands to adapt to varying data states, ensuring optimal identification accuracy for each read operation.
2Measurement precision
If set features commands are sent for each read operation to modify read thresholds, then read accuracy is improved, but device performance deteriorates
Solution Approach 1:
The set features command is executed in advance before the read operation to pre-establish the optimal read threshold. This preliminary action ensures accuracy is achieved without compromising overall device performance during the read process itself.
Solution Approach 2:
The patent changes the read voltage threshold parameter dynamically by issuing set features commands with modified threshold values. This allows the system to adapt to different data states and maintain high read accuracy while managing performance through controlled parameter adjustment.
3Measurement precision
If set features commands are repeatedly sent with identical threshold offsets, then threshold accuracy is maintained, but bus utilization efficiency decreases
Solution Approach 1:
The patent implements feedback by monitoring whether the read voltage threshold has actually changed between operations. The set features command is only issued when the threshold parameter has changed, preventing redundant commands from being sent over the bus and improving utilization efficiency.
Solution Approach 2:
Instead of sending set features commands for every read operation, the patent applies partial action by only issuing commands when necessary - specifically when the threshold offset has changed. This reduces unnecessary bus traffic while maintaining threshold accuracy when needed.
Data Source
AI summary
Aspects of a storage device including a memory and a controller are provided which prevent retransmissions of set features commands with identical read voltage threshold offsets for the same die. When the controller receives a first read command for data stored in the memory, the controller identifies a first parameter to modify a first read threshold, and executes a first set features command for modifying the read threshold based on the first parameter. Subsequently, when the controller receives a second read command from the host device for data stored in the memory, the controller identifies a second parameter to modify a second read threshold, and determines whether the first and second parameters are the same. If the parameters are the same, the controller refrains from executing a second set features command for modifying the second read threshold. Thus, the read latency of the storage device may be reduced.