Virtual Zone Wear Leveling for Non-Volatile Memory Block Uniformity
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Solution Overview
Problem
Non-volatile memory devices face inefficiencies in managing block erase counts, leading to uneven wear and reduced performance due to the lack of effective wear leveling mechanisms, which results in excessive degradation of specific blocks.
Innovation Solution
A virtual zone management method is introduced, where a storage controller divides blocks into zones and performs wear leveling by replacing blocks with high erase counts in one zone with those having low erase counts in another zone, using a flash translation layer structure that includes address mapping tables and a wear leveling manager to maintain uniform erase counts across zones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wear leveling is not implemented, then the device complexity is reduced, but the reliability deteriorates due to uneven block degradation
Solution Approach 1:
The patent divides the flash memory into multiple zones based on erase count characteristics, creating distinct regions (first zone with high erase count, second zone with low erase count). This segmentation allows independent management of worn and fresh blocks, enabling wear leveling without requiring complex global management of all blocks.
Solution Approach 2:
Different zones are assigned different management strategies based on their local characteristics. The first zone (high erase count) and second zone (low erase count) receive tailored replacement policies, where blocks are replaced preferentially from the first zone to maintain uniform wear across the entire device.
2Reliability
If blocks are frequently replaced to maintain uniform erase counts, then the reliability is improved, but the productivity deteriorates due to increased replacement operations
Solution Approach 1:
By segmenting blocks into zones based on erase count, the patent reduces the search space for replacement candidates from all blocks to only those in the first zone. This segmentation enables more efficient selection of replacement blocks without requiring full-device scans.
Solution Approach 2:
The patent performs preliminary classification of blocks into zones based on erase count characteristics. This preliminary action organizes blocks before replacement operations, making the subsequent replacement process more efficient by directly targeting blocks in the first zone that need replacement.
3Measurement precision
If the flash translation layer includes comprehensive mapping information, then the measurement precision of address mapping is improved, but the device complexity increases due to additional management structures
Solution Approach 1:
The patent segments the address mapping management by creating separate logical address ranges for different zones. The first logical address range maps to the first zone and the second logical address range maps to the second zone, simplifying the mapping management while maintaining precision.
Solution Approach 2:
Different mapping strategies are applied to different zones based on their characteristics. The mapping manager maintains separate mapping information for each zone, allowing optimized management of address translations tailored to each zone's erase count profile.
Data Source
AI summary
A storage device includes a non-volatile memory including a plurality of blocks, and a storage controller configured to divide the plurality of blocks into a plurality of zones, determine a first zone of the plurality of zones corresponding to a logical address received from a host, based on a value of the logical address, map the logical address to a physical address corresponding to a first block in the first zone, and replace at least one of the logical address or the first block with a logical address or a block of a second zone of the plurality of zones. The second zone is different from the first zone.