WriteBooster Buffer Segmentation for UFS Preserve User Space
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Solution Overview
Problem
The WriteBooster feature in UFS devices faces performance degradation when the WriteBooster buffer is merged into user space, leading to increased Program/Erase cycles and reduced endurance of SLCs, especially in Preserve User Space mode.
Innovation Solution
Implementing a method and system to intelligently merge portions of the WriteBooster buffer into user space based on the remaining lifetime of SLCs, prioritizing those with the lowest Program/Erase cycles, thereby maintaining performance and extending the lifespan of the SLCs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the WriteBooster buffer is merged into user space in Preserve User Space mode, then the total user space capacity is maintained, but the write performance degrades due to internal data structure adjustments and buffer flushing requirements
Solution Approach 1:
The write buffer is segmented into multiple portions based on the remaining lifetime of SLCs within the buffer. This segmentation allows the system to selectively merge only the portions with lowest remaining lifetime into user space, while preserving the performance benefits of the write buffer for portions with higher remaining lifetime. The segmentation resolves the contradiction by enabling partial merging that maintains both user space capacity and write performance.
Solution Approach 2:
Different portions of the write buffer are treated differently based on their local characteristics (remaining lifetime of SLCs). Portions with lower remaining lifetime are prioritized for merging into user space, while portions with higher remaining lifetime continue to function as performance-optimized write buffer. This local differentiation resolves the contradiction by applying merging only where necessary to maintain user space capacity without compromising overall write performance.
2Quantity of substance
If the WriteBooster buffer is merged into user space, then the user space capacity is preserved, but the endurance of SLCs is reduced due to increased Program/Erase cycles
Solution Approach 1:
The system performs preliminary assessment of SLC remaining lifetime before merging buffer portions into user space. By identifying and merging only the portions with lowest remaining lifetime, the system performs a preliminary triage that protects the majority of SLCs from additional wear. This preliminary action resolves the contradiction by ensuring that merging operations are performed selectively to preserve SLC endurance while maintaining user space capacity.
Solution Approach 2:
The system discards (merges into user space) only the portions of the write buffer with lowest remaining lifetime, while recovering and preserving the functional integrity of portions with higher remaining lifetime. This selective discarding approach resolves the contradiction by minimizing the impact on SLC endurance while still achieving the goal of preserving user space capacity.
3Productivity
If the WriteBooster buffer is maintained separately from user space, then the write performance is optimized with low latency, but the total physical storage available for user space is reduced
Solution Approach 1:
The system dynamically adjusts the separation between the write buffer and user space based on operational conditions. When user space capacity is sufficient, the write buffer is maintained separately to optimize write performance. When user space becomes full, the system dynamically merges portions of the write buffer into user space to preserve capacity. This dynamic adjustment resolves the contradiction by adapting the buffer configuration to current storage needs while maintaining performance optimization.
Data Source
AI summary
In a flash memory device, portions of a write buffer may be merged into a user space logical unit based on a measurement of write buffer usage. In a Universal Flash Storage (UFS) device configured with the WriteBooster feature, the write buffer may be a WriteBooster buffer. When it is determined that a user space logical unit has become full, then the write buffer usage may be determined. Portions of the write buffer that are least used or have the longest remaining lifetime may be preferentially merged into the user space logical unit.