Background Memory Scan Block Selection by Page Fill Ratio
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Solution Overview
Problem
In memory sub-systems with zoned namespaces, traditional Logical to Physical (L2P) mapping schemes are not applicable, leading to complexities in background scan operations due to partially filled zones and varying block stripe sizes.
Innovation Solution
The memory sub-system selects a memory block for scans based on the highest page fill ratio, identifying block stripes across logical units, determining their fill ratios, and choosing the block stripe with the highest fill ratio for the scan operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If traditional L2P mapping schemes are used, then memory management is simplified, but background scan operations become complex due to partially filled zones and varying block stripe sizes
Solution Approach 1:
The patent changes the selection criterion from traditional L2P mapping-based approaches to page fill ratio-based selection. By using fill ratio as a new parameter to identify blocks for scanning, the system adapts to zoned namespace characteristics where zones can be partially filled and block stripe sizes vary, thereby resolving the complexity in background scan operations while maintaining adaptability to the zoned structure.
2Productivity
If all blocks are scanned uniformly, then scan operation simplicity is maintained, but memory scan efficiency decreases due to partially filled zones
Solution Approach 1:
The patent applies local quality by selecting blocks for scanning based on their specific page fill ratios rather than treating all blocks uniformly. Blocks with higher fill ratios are prioritized for scanning, as they contain more valid data and are more likely to reveal actual errors. This localized approach to block selection maintains scan operation simplicity while significantly improving memory scan efficiency in zoned namespace environments.
3Productivity
If blocks with highest page fill ratio are selected for scans, then memory scan efficiency is improved, but block selection complexity increases
Solution Approach 1:
The patent implements feedback by using the page fill ratio as a measurable characteristic that reflects the actual data distribution in zoned namespace blocks. The fill ratio is calculated based on the number of valid pages in each block, providing a feedback mechanism that guides block selection. This feedback approach simplifies the identification process by using a direct, quantifiable metric (fill ratio) rather than complex analysis, thereby improving scan efficiency without excessively increasing block selection complexity.
Data Source
AI summary
The memory sub-systems of the present disclosure selects, for memory scans, a memory block which has a highest page fill ratio. In one embodiment, the memory sub-system identifies a number of block stripes located on a logical unit (LU) identified by a logical unit number (LUN), where the LU is one of a plurality of LUs of a memory device. The sub-system determines a fill ratio for each of the plurality of block stripes. The sub-system selects, among the block stripes, a block stripe with a highest fill ratio. The sub-system identifies, from the selected block stripe, a memory block of the LU. The sub-system performs a memory scan operation on the memory block of the memory device.