Leveraging Static and Dynamic Wear Leveling to Prolong the Lifespan of Solid-State Drives

Abstract

In order to extend the lifespan of SSDs, it is essential to achieve wear leveling that evenly distributes the accumulated erase counts of NAND blocks, thereby delaying the occurrence of bad blocks as much as possible. This paper proposes the Greedy-MP policy, integrating static and dynamic wear leveling. When a specific block exhibits excessive erasures surpassing a defined threshold, Greedy-MP initiates the migration of cold data, expected to undergo infrequent modifications, to that block. Additionally, migrated blocks are excluded as candidates for garbage collection until their erase counts reach a similar level to others, preventing premature transition into bad blocks. Performance evaluations demonstrate that Greedy-MP achieves the longest lifespan across all test scenarios. Compared to policies solely utilizing static wear leveling like PWL, it extends the lifespan by up to 1.72 times. Moreover, when integrated with dynamic wear leveling policies such as CB alongside static wear leveling like PWL, it extends the lifespan by up to 1.99 times. Importantly, these extensions are achieved without sacrificing performance. By preserving garbage collection efficiency, Greedy-MP delivers the shortest average response time for I/O requests.

Keywords

• erase count
• lifespan
• NAND
• solid-state drives
• wear leveling