Extending SSD Lifetime via Balancing Layer Endurance in 3D NAND Flash Memory

By stacking layers vertically, 3D flash memory enables continuous growth in capacity. In this paper, we study the layer variation in 3D flash blocks and find that bottom layer pages exhibit the lowest endurance, whereas middle layer pages demonstrate the highest endurance. The imbalanced endurance across different layers will diminish the overall SSD lifetime. To address this issue, we introduce a novel layer-aware write strategy, named LA-Write. It performs write-skip operations with layer-specific probabilities. The endurance of bottom layer pages with the highest probability would be noticeably improved, which could balance the layer endurance. Experiment results show that LA-Write can improve SSD lifetime by 29%.