# Leveraging Static and Dynamic Wear Leveling to Prolong the Lifespan of Solid-State Drives
## 5 Conclusions  
We proposed the Greedy-MP wear leveling policy, which utilizes both static and dynamic wear leveling. Greedy-MP is based on PWL static wear leveling, where if the accumulated erase count of a specific block exceeds a threshold, migration is performed to move valid pages from the youngest block to a worn-out block. Additionally, as a victim block selection policy for garbage collection, Greedy-MP operates a greedy policy but manages worn-out migration blocks separately to avoid selecting worn-out blocks as victims of garbage collection, thus delaying the conversion of worn-out blocks to bad blocks as much as possible. Simulation results using the SSDSim simulator and MSRC server traces demonstrated the following:  
* Greedy-MP achieved the longest lifespan across all traces. Compared to policies using only PWL, it extended lifespan by up to 1.72 times, and compared to policies using PWL with CB dynamic wear leveling, it extended lifespan by up to 1.99 times, and compared to policies using PWL with WOGC dynamic wear leveling, it extended lifespan by up to 3.56 times. * In Greedy-MP policy, the average erase count of all blocks approached the maximum possible value when the SSD lifespan terminated, indicating that wear leveling had almost reached its limit. * Greedy-MP achieved the shortest average response time of input/output requests, indicating no significant performance degradation. * Using static wear leveling, like PWL, alongside dynamic wear leveling, like CB or WOGC, was more effective in extending SSD lifespan than using dynamic wear leveling alone. * Comparing policies using dynamic wear leveling alone (CB, WOGC) to those using only static wear leveling (PWL), the latter was largely more effective in extending SSD lifespan. However, combining both can enhance wear leveling degree, suggesting that it is desirable to utilize both static and dynamic wear leveling when designing new wear leveling policies. Figure 10: Comparison of Average Response Time of Host Requests (PWL, CB+PWL, WOGC+PWL, GREEDY-MP). (**a**) cam01; (**b**) hm0; (**c**) prn0; (**d**) proj0; (**e**) stga; (**f**) weba. * [PERSON] et al. (2015) [PERSON]; [PERSON]; [PERSON]; [PERSON] PWL: A progressive wear leveling to minimize data migration overheads for NAND flash devices. In Proceedings of the DATE, Grenoble, France, 9-13 March 2015; pp. 1209-1212. * [PERSON] and [PERSON] (2011) [PERSON]; [PERSON] Implementing greedy replacement scheme using multiple List for page mapping scheme. _J. KIIT_**2011**, _17_, 17-23. * [PERSON] (1995) [PERSON] Flash File System. United States US5404485A, 4 April 1995. * [PERSON] (1999) [PERSON] Flash File System Optimized for Page-Mode Flash Technologies. United States US5937425A, 10 August 1999. * [PERSON] et al. (2002) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] A space-efficient flash translation layer for compactflash systems. _IEEE Trans. Consum. Electron._**2002**, \(2\), 366-375. [CrossRef]
* [PERSON] et al. (2007) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] A log buffer-based flash translation layer using fully-associative sector translation. _ACM Trans. Embed. Comput. Syst. (TECS)_**2007**, \(6\), 18-es. [CrossRef]
* [PERSON] and [PERSON] (2014) [PERSON]; [PERSON] Active log pool for fully associative sector translation. _IEICE Electron. Express_**2014**, _11_, 20130942. [CrossRef]
* [PERSON] et al. (2022) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] GuardedErase: Extending SSD lifetimes by protecting weak wordlines. In Proceedings of the USENIX FAST, Santa Clara, CA, USA, 22-24 February 2022; pp. 133-146. * [PERSON] et al. (2016) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; et al. 256 Gb 3b/Cell V-NAND flash memory with 48 stacked wl layers. In Proceedings of the IEEE ISSCC, San Francisco, CA, USA, 31 January-4 February 2016; pp. 130-132. * [PERSON] et al.