SAW: System-assisted wear leveling on the write endurance of NAND flash devices

The write endurance of NAND flash memory adversely impacts the lifetime of flash devices. A flash cell is likely to wear out after undergoing excessive program/erase (P/E) flips. Wear leveling is hence employed to spread erase operations as evenly as possible. It is traditionally conducted by the flash translation layer (FTL), a management firmware residing in flash devices. In this paper, we shall propose a novel wear leveling algorithm involving the operating system (OS). We will show that our operating System-Assisted Wear leveling (SAW) algorithm can significantly improve the wear evenness. SAW takes advantage of OS's knowledge about files at a higher level of abstraction, and provides useful hints to the lower-level FTL to accommodate data. A prototype based on a file system and an FTL has been developed to verify the effectiveness of SAW. Experiments show that wear evenness can be improved by as much as 85.0% compared to the state-of-the-art FTL wear leveling schemes.