Flash Memory Management via Sector Pointer Mapping
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Solution Overview
Problem
Flash memory devices face significant degradation in write speed and increased P/E cycling due to the need to rewrite entire erase units when only a single sector is modified, leading to inefficient memory management and limited RAM capacity in devices like SD cards.
Innovation Solution
A method involving a data management structure with a metadata buffer that creates pointers for each data sector, allowing for merging of data sectors within the same erase unit and optimizing write operations by distinguishing between random and sequential data access, thereby reducing unnecessary writes and improving write speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the controller manages memory at the erase unit level to use smaller RAM, then the RAM memory size is reduced, but the write speed degrades significantly due to frequent rewriting of entire erase units
Solution Approach 1:
The patent segments the mapping structure into two parts: a small RAM-based cache for recently accessed logical-to-physical address mappings, and a larger flash-based storage for the complete mapping table. This segmentation allows the controller to maintain fast access for frequent operations while storing comprehensive mapping information, resolving the contradiction between limited RAM size and the need for efficient address translation during writes.
Solution Approach 2:
The patent implements preliminary action by pre-allocating and pre-mapping logical sectors to physical erase units before actual write operations occur. The mapping table is prepared in advance in flash memory, and the RAM cache is pre-loaded with relevant mappings, so that when a write operation occurs, the controller can immediately proceed without needing to perform complex address translation or erase entire units on the fly.
2Adaptability or versatility
If random write operations are performed on flash memory, then data access flexibility is improved, but the number of P/E cycles increases significantly
Solution Approach 1:
The patent introduces an intermediary mapping layer between the logical address space and the physical flash memory structure. This mapping table acts as a mediator that translates random logical write requests into sequential or optimized physical write operations. By decoupling the logical address space from the physical erase unit structure, the system maintains random write flexibility while enabling more efficient physical write patterns that reduce P/E cycling.
Solution Approach 2:
The patent dynamically changes the mapping parameters based on access patterns. When random writes are detected, the system adjusts the mapping strategy to consolidate writes into fewer erase units. The mapping table is updated to reflect changed access patterns, allowing the system to transition from random access to more sequential write patterns physically, thereby reducing the number of program-erase cycles required.
3Reliability
If the entire erase unit is rewritten when a single sector is modified, then data integrity is maintained, but the write operation efficiency decreases
Solution Approach 1:
The patent extracts the address mapping information from the bulk erase unit structure and stores it separately in a dedicated mapping table. This allows the mapping metadata to be updated independently of the actual data sectors. When a single sector is modified, only the relevant mapping entry needs to be updated in the mapping table, while the physical erase unit can be rewritten more efficiently without requiring complete re-erasure, thus maintaining data integrity while improving write efficiency.
Data Source
AI summary
A method, a computer readable medium and a system for managing flash memory. The method may include receiving multiple data sectors from an interface; writing the multiple data sectors into a data buffer that is nonvolatile; creating a pointer in a data management structure that is stored in a metadata buffer that is nonvolatile, for each data sector corresponding to a storage location of the data sector in the data buffer; if a predefined condition is reached, merging data sectors stored in the data buffer with data sectors that are already stored in a sequential nonvolatile portion of the flash memory device, wherein the sequential nonvolatile portion differs from the data buffer.