SSD Memory Block Endurance Management via Segmented Garbage Collection
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Solution Overview
Problem
Flash-based SSD devices face limited write-erase cycle count and uneven wear-out of memory blocks due to 'write amplification' and inefficient wear-leveling, leading to reduced endurance lifetime.
Innovation Solution
A memory management system that dynamically sorts free memory blocks by write-erase endurance cycle count, separates user-write and relocation data, and implements a windowed garbage collection process to balance block usage and reduce write amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If relocate-on-write is used for performance reasons, then I/O performance is improved, but write amplification increases and endurance lifetime decreases
Solution Approach 1:
The patent segments free memory blocks into different categories (young blocks and old blocks) based on their endurance characteristics, and segments data into user data and relocation data. This segmentation allows differential placement strategies that reduce overall write amplification while maintaining performance.
Solution Approach 2:
The patent applies local quality by placing user data preferentially on young blocks (with higher remaining endurance) and relocation data on old blocks (with lower remaining endurance). This localized quality assignment optimizes the overall system endurance by matching data types with appropriate block characteristics.
2Reliability
If wear-leveling techniques are used to exhaust cycle budget of blocks, then endurance is maximized, but wear-leveling insufficiency occurs when garbage collection cannot return free blocks
Solution Approach 1:
The patent implements dynamic block management where the system continuously monitors block status and dynamically adjusts data placement strategies. The free block pool is dynamically updated based on garbage collection results, allowing the system to adapt to changing block availability and prevent wear-leveling insufficiency.
Solution Approach 2:
The patent employs feedback mechanisms where garbage collection results feed back into the free block pool management. The system monitors the state of free blocks and uses this information to adjust wear-leveling operations, ensuring that wear-leveling continues effectively even under heavy workload conditions.
3Reliability
If static wear-leveling forces migration of cold data from new blocks to old blocks, then uneven wear-out is addressed, but write amplification increases due to frequent cold data movement
Solution Approach 1:
The patent applies local quality by differentiating between user data and relocation data, and by differentiating between young blocks and old blocks. Cold data (relocation data) is preferentially placed on old blocks, reducing the need for frequent migrations and thereby reducing write amplification while maintaining even wear distribution.
4Device complexity
If free memory blocks are not sorted by endurance cycle count, then data placement is simpler, but uneven wear-out occurs and endurance lifetime is reduced
Solution Approach 1:
The patent applies preliminary action by pre-sorting free memory blocks in the free block pool according to their endurance cycle count before data placement occurs. This preliminary organization enables simple, efficient data placement operations that automatically achieve even wear distribution without complex real-time decision-making.
Data Source
AI summary
A memory management system and method for managing memory blocks of a memory device of a computer. The system includes a free block data structure including free memory blocks for writing, and sorting the free memory blocks in a predetermined order based on block write-erase endurance cycle count and receiving new user-write requests to update existing data and relocation write requests to relocate existing data separately, a user-write block pool for receiving youngest blocks holding user-write data (i.e., any page being updated frequently) from the free block data structure, a relocation block pool for receiving oldest blocks holding relocation data (i.e., any page being updated infrequently) from the free block data structure, and a garbage collection pool structure for selecting at least one of user-write blocks and relocation blocks for garbage collection, wherein the selected block is moved back to the free block data structure upon being relocated and erased.