A flash resident file system for embedded sensor networks

Many embedded devices, especially those designed for environmental sensor logging, have extremely limited RAM, often less than several kilobytes. Logged data is stored on flash memory and needs to be easily managed at low energy cost. A file system is required to efficiently manage the device, specifically dealing with wear leveling of the flash memory. Previous flash file systems, even those designed for small memory devices, still consume a reasonable amount of RAM (1K or more). In this paper, we present a flash file system that supports record level consistency with the entire file system and address mapping functionality stored on flash memory. Although this results in a marginally higher read cost, RAM utilization is less than 150 bytes and the read cost in terms of energy usage is less. The key idea is that NOR flash used on these devices supports direct byte reads not supported by NAND memory which allows page translation and data storage to require less memory and consume less energy.