Wear Leveling via Smallest Physical Block Number Selection
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Solution Overview
Problem
Non-volatile memory (NVM) devices, such as flash memory, have a limited number of erase cycles, leading to premature failure if blocks are not used evenly, resulting in a shortened device lifetime.
Innovation Solution
A method of wear leveling that maintains a management table to select and utilize spare blocks with the smallest physical block numbers as temporary blocks for data storage, ensuring even usage and extending the device's lifespan by dynamically switching blocks between spare and data states based on usage patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If blocks are not used evenly in NVM devices, then the device complexity is reduced (no wear leveling needed), but the reliability deteriorates (premature failure due to limited erase cycles)
Solution Approach 1:
The patent changes the parameter selection criterion from erase count to physical block number. By selecting spare blocks with the smallest physical block numbers as temporary blocks, the system achieves wear leveling without requiring complex erase count tracking and comparison operations, thus improving reliability while reducing operational complexity
Solution Approach 2:
The physical block number itself serves as the selection criterion, eliminating the need for additional wear leveling logic. The system automatically achieves even block usage through this simple parameter-based selection, making the wear leveling process self-service and reducing overall system complexity
2Reliability
If a complex wear leveling procedure is implemented to extend device lifetime, then the reliability improves, but the productivity deteriorates (slower block selection and data writing)
Solution Approach 1:
The patent changes the selection parameter from erase count (requiring reading, comparing, and updating) to physical block number (requiring only reading and comparing). This parameter substitution dramatically speeds up the block selection process while maintaining wear leveling effectiveness, thus improving productivity without sacrificing reliability
Solution Approach 2:
The patent extracts the essential wear leveling function from complex erase count management and implements it through simple physical block number-based selection. This extraction removes unnecessary complexity and operational overhead, achieving both extended device lifetime and faster block selection
3Duration of action of stationary object
If erase cycles are limited in NVM blocks, then the manufacturing precision is improved (controlled degradation), but the duration of action deteriorates (shorter device lifetime)
Solution Approach 1:
The patent changes the block selection parameter to physical block number, which enables systematic distribution of write operations across all blocks. This parameter change ensures that the limited quantity of erase cycles is distributed evenly across all blocks, maximizing the duration of action (device lifetime) without requiring additional cycle management
Data Source
AI summary
A method of wear leveling for a data storage device is provided. The data storage device includes a non-volatile memory having a plurality of blocks. A portion of the blocks not having any valid data are defined as spare blocks, and the spare blocks are associated with a spare pool. The method includes the steps of: maintaining a management table recording a plurality of physical block numbers and a plurality of block statuses corresponding to the blocks; selecting a first spare block having a first smallest physical block number as a current temporary block; receiving a write command from a host; determining whether data in the write command shall be written into the current temporary block; if false, selecting a second spare block having a second smallest physical block number as a next temporary block; and writing the data into the next temporary block.