Dual L2P Mapping Tables for Faster NVM Address Lookup
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Solution Overview
Problem
Existing tree structured logical-to-physical (L2P) data structures in memory devices suffer from increased delays and management complexity as storage density increases, leading to longer lookup times and complex memory management schemes.
Innovation Solution
Implementing a dual L2P mapping table structure, where a first L2P mapping table includes logical block addresses and a second L2P mapping table includes physical block addresses, both of the same size, utilizing two hash functions for efficient LBA to PBA translations, reducing the number of data structures needed as storage density increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tree structured L2P data structure is used, then the mapping between LBAs and PBAs can be stored, but the lookup time increases and management complexity increases as storage density increases
Solution Approach 1:
The patent divides the L2P mapping into two separate tables: a first L2P table storing LBA to PBA mappings, and a second L2P table storing PBA to logical address mappings. This segmentation allows each table to be optimized independently and reduces the search path length compared to a single tree structure, thereby reducing lookup time while maintaining mapping reliability.
Solution Approach 2:
The patent extracts the L2P mapping function from a complex tree structure and implements it using two simpler hash tables. By taking out the mapping capability and re implementing it with a different data structure (hash tables instead of trees), the solution eliminates the overhead of tree traversal while maintaining the essential mapping function.
2Reliability
If a tree structured L2P data structure is used, then the mapping between LBAs and PBAs can be stored, but the management complexity increases as storage density increases
Solution Approach 1:
The patent segments the L2P management into two independent tables with distinct functions. The first table handles LBA to PBA translation, while the second table handles PBA to logical address translation. This segmentation simplifies management by allowing each table to be independently optimized and maintained, reducing the overall management complexity compared to a single tree structure.
Solution Approach 2:
The patent replaces the mechanical tree traversal system with a hash table-based system. Hash tables provide O(1) average case lookup time compared to O(log n) for trees, and the hash function-based access pattern simplifies management operations. The substitution of the data structure mechanism fundamentally reduces management complexity while maintaining mapping reliability.
3Quantity of substance
If storage density increases, then more data can be stored, but the number of levels in L2P data structure increases leading to longer lookup delays
Solution Approach 1:
The patent segments the mapping function into two tables that can scale independently. As storage density increases and more data needs to be mapped, each table can be optimized separately to handle the increased capacity without increasing the lookup path length. The dual-table structure allows for more efficient scaling compared to a single tree structure where additional levels would be required.
Solution Approach 2:
The patent changes the fundamental parameter of data structure from a tree (where depth increases with capacity) to a hash table (where lookup time remains constant regardless of capacity). This parameter change allows the system to accommodate increased storage density without increasing lookup delay, as hash tables provide constant time lookup independent of the number of entries.
Data Source
Figure 1
Figure 2~3A
Figure 3B~3C
AI summary
An example apparatus comprises a controller coupled to a non-volatile memory (NVM) device. The controller may be configured to cause a logical block address (LBA) to be stored in a first logical-to-physical (L2P) data structure in the NVM device and a physical block address (PBA) to be stored in a second L2P data structure in the NVM device. The first L2P data structure and the second L2P data structure may have a same size associated therewith.