Host FTL Block Assignment for SSD Wear Leveling
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Solution Overview
Problem
Open-channel SSDs face reduced lifespan and data reliability due to ineffective wear-leveling processes, as they frequently assign blocks with high erase counts for data write operations, leading to uneven wear distribution and premature degradation.
Innovation Solution
A host system with a host flash translation layer (FTL) manages block assignments based on erase count values, using a block assignment module to prioritize free blocks with lower erase counts for data write operations, thereby equalizing erase counts across blocks and extending the SSD's lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If free blocks are assigned for data write operations without considering erase count values, then the data write operation can be performed quickly, but the wear distribution becomes uneven and the SSD lifespan is reduced
Solution Approach 1:
The patent changes the selection criterion parameter from simple availability to erase count value-based priority, where blocks are selected based on their erase count rather than just being any available free block. This parameter change enables wear-leveling while maintaining write operation efficiency.
Solution Approach 2:
The patent replaces the simple first-come-first-served block assignment mechanism with a priority-based selection mechanism that uses erase count values to determine which free block to assign next, thereby substituting a naive allocation strategy with a wear-aware allocation strategy.
2Device complexity
If wear-leveling operations are not performed in open-channel SSD environments, then the system complexity is reduced, but the lifespan of the SSD is reduced and data reliability deteriorates
Solution Approach 1:
The host system performs wear-leveling operations autonomously by maintaining and querying erase count values itself, rather than relying on the SSD controller to manage wear. This self-service approach enables wear-leveling in open-channel SSD environments where the controller provides minimal functionality.
Solution Approach 2:
The system implements feedback by continuously querying erase count values from the SSD and using this information to make informed decisions about which free blocks to assign for data writes, creating a closed-loop wear-management system.
3Quantity of substance
If blocks with high erase counts are assigned for data write operations, then more free blocks are available for assignment, but the wear distribution becomes uneven leading to premature degradation
Solution Approach 1:
The patent creates equipotentiality in wear distribution by selecting free blocks with the lowest erase counts for assignment, ensuring that all blocks experience similar wear levels over time. This equalizes the 'wear potential' across all blocks in the SSD.
Data Source
AI summary
A host system configured to communicate with a storage system, including a host flash translation layer (FTL) configured to manage a plurality of blocks included in the storage system, wherein the host FTL includes a block assignment module configured to generate priority information indicating priorities of free blocks from among the plurality of blocks based on erase count values of the free blocks, and wherein the host FTL is configured to assign a free block having a lowest erase count value, from among the free blocks, for a data write operation based on the priority information; a counting circuit configured to count a number of erase operations performed on each of the plurality of blocks; and an interface circuit configured to transmit to the storage system a block address along with an access request to the storage system, the block address indicating a position of the assigned free block.