Nonvolatile Memory Block Group Construction for Defect Management
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Solution Overview
Problem
In memory systems using nonvolatile memory, such as SSDs with NAND flash memory, the uneven distribution of defective blocks across dies or planes leads to inefficient use of non-defective blocks, resulting in reduced available storage capacity and increased management burden.
Innovation Solution
The implementation of a memory system that constructs block groups using both first and second type block groups, where the first type block groups consist of an equal number of non-defective blocks from each die or plane, and the second type block groups select more non-defective blocks from dies or planes with fewer defects, ensuring all non-defective blocks are utilized, even when defect distribution is uneven.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If blocks are selected as access units from different dies, then parallel access capability is improved, but the number of unused non-defective blocks increases when defect distribution is uneven
Solution Approach 1:
The patent applies local quality by creating different types of block groups with different compositions. First type block groups are formed with equal numbers of blocks from each die for balanced parallel access, while second type block groups are formed to utilize remaining non-defective blocks from dies with fewer defects. This localized differentiation allows the system to optimize for both parallel access speed and complete utilization of non-defective blocks.
Solution Approach 2:
The patent segments the block groups into two distinct types based on their composition and usage. First type block groups are segmented for primary parallel access operations with equal block distribution across dies, while second type block groups are segmented to capture and utilize remaining non-defective blocks. This segmentation resolves the contradiction by creating specialized groups for different purposes.
2Quantity of substance
If multiple block types are constructed to utilize all non-defective blocks, then storage capacity is improved, but zone management complexity increases
Solution Approach 1:
The patent changes the parameters of block group construction by defining two distinct types with different composition rules. First type block groups use equal block counts from each die, while second type block groups adjust block counts based on remaining non-defective blocks. This parameter change allows maximum storage capacity utilization while maintaining manageable complexity through clear, rule-based construction methods.
Data Source
AI summary
According to one embodiment, a controller constructs a plurality of block groups. The plurality of block groups include at least a first block group configured using a first type block group and a second block group configured using a second block group. The first type block group includes a plurality of non-defective blocks obtained by selecting one or more non-defective blocks in an equal number from each of a plurality of dies or each of a plurality of planes. The second type block group includes a plurality of non-defective blocks. The number of non-defective blocks included in the second type block group is equal to the number of non-defective blocks included in the first type block.