SSD Patrol Read Using Word Line Grouping and Representative Reads
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Solution Overview
Problem
Conventional solid-state storage devices face inefficiencies in patrol read operations due to frequent updates of read threshold voltages across word lines, leading to conflicts with write and read operations, and the grouping method does not ensure compatibility within word line groups, resulting in reduced performance.
Innovation Solution
A solid-state storage device and patrol read method that classifies word lines into groups based on read threshold voltage using a neural network, setting a representative word line for each group, and updates the threshold voltage only when necessary, reducing the need to read all word lines during patrol operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If each word line is read one by one during patrol read operation, then the read threshold voltage can be accurately determined for each word line, but the operation time is excessive and conflicts with write and read operations
Solution Approach 1:
The patent divides all word lines into multiple groups based on their read threshold voltage characteristics. Instead of processing each word line individually, the system processes groups of word lines together, significantly reducing the total number of patrol read operations required while maintaining accurate threshold voltage determination through representative word line selection.
Solution Approach 2:
The patent performs patrol read operations on only a subset of word lines (specifically, representative word lines from each group) rather than all word lines. This partial action approach is sufficient to determine threshold voltage updates for entire groups, reducing operation time while maintaining measurement accuracy through intelligent sampling.
2Quantity of substance
If word lines are grouped and use common read threshold voltage, then memory space is reduced, but the grouping does not guarantee compatibility and causes frequent invalid updates
Solution Approach 1:
The patent applies local quality by assigning read threshold voltages based on local characteristics of word lines. Word lines with similar threshold voltage characteristics are grouped together and share common threshold voltages, while groups with different characteristics maintain separate threshold voltages. This ensures compatibility within groups while optimizing memory space usage.
Solution Approach 2:
The patent dynamically adjusts the grouping parameters and threshold voltage values based on actual read operations and error detection. When threshold voltage characteristics change, the system updates groupings and threshold values accordingly, ensuring ongoing compatibility and reliability while maintaining space efficiency.
3Measurement precision
If read threshold voltage is updated frequently in conventional patrol read, then measurement accuracy is maintained, but conflicts with write and read operations increase, reducing device performance
Solution Approach 1:
The patent merges multiple word line threshold voltage updates into single group-level updates. By determining threshold voltage requirements at the group level rather than individual word line level, the system reduces the frequency of update operations while maintaining measurement precision through representative sampling, thereby improving overall device performance.
Solution Approach 2:
The patent implements feedback mechanisms where patrol read operations on representative word lines provide information about threshold voltage accuracy for entire groups. This feedback drives selective updates only when and where needed, maintaining measurement precision while minimizing disruptive update operations that would conflict with normal read and write operations.
Data Source
AI summary
A solid-state storage device is provided, which includes a controller and a non-volatile memory. The controller selects a first word line group from a plurality of word line groups obtained by classifying the word lines based on a read threshold voltage of each word line, and a representative word line corresponding to each word line group is set based on the read threshold voltage associated with each word line group. The controller uses the read threshold voltage of a first representative word line corresponding to the first word line group to read page data of the first representative word line. When the controller cannot correctly read the page data of the first representative word line using the read threshold voltage of the first representative word line, the controller updates the read threshold voltage of the first representative word line in the first word line group.