Background Memory Scan Block Selection by Page Fill Ratio
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Solution Overview
Problem
In zoned namespaces SSDs, traditional background scan operations are complicated by the absence of Logical to Physical mapping, leading to partially filled blocks and increased complexity due to smaller zone sizes, which affect the efficiency of memory scans.
Innovation Solution
The memory sub-system selects a candidate memory block with the highest page fill ratio for memory scans by identifying block stripes with the highest fill ratio and performing scans on these blocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional background scan operations are used in zoned namespaces SSDs, then memory scans can be performed, but the operations become complicated by the absence of Logical to Physical mapping, leading to partially filled blocks and increased complexity
Solution Approach 1:
The patent changes the selection criterion from traditional scan methods to filling ratio-based selection. By calculating and comparing filling ratios of different blocks, the system automatically identifies the most suitable block for scanning, transforming the complex manual selection process into an automated parameter-driven decision-making process that simplifies operations while maintaining reliability
Solution Approach 2:
The system performs self-service by automatically selecting the optimal block for scanning based on its own filling ratio characteristics. The memory subsystem evaluates its own state and makes intelligent decisions about which block to scan without external intervention, reducing operational complexity while ensuring accurate results
2Adaptability or versatility
If zone sizes are made smaller to support zoned namespaces, then namespace management is improved, but block fill ratios decrease and scan efficiency is reduced
Solution Approach 1:
The patent introduces filling ratio as a new selection parameter to compensate for smaller zone sizes. By calculating the ratio of filled pages to total pages in each block and selecting blocks with the highest filling ratios, the system maintains scan efficiency despite the reduced zone dimensions, effectively decoupling scan performance from zone size
3Productivity
If blocks with lower filling ratios are scanned, then more blocks are available for scanning, but bit error rate detection accuracy decreases due to partially filled pages
Solution Approach 1:
The patent changes the selection parameter from arbitrary block selection to filling ratio-based selection. By calculating and comparing filling ratios, the system identifies blocks with the highest proportion of fully filled pages, ensuring that scanning operations maintain high measurement precision for bit error rate detection while still providing productive scan throughput
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.