A transactional flash file system for microcontrollers

Abstract

We present a transactional file system for flash memory devices. The file system is designed for embedded microcontrollers that use an on-chip or on-board NOR flash device as a persistent file store. The file system provides atomicity to arbitrary sequences of file system operations, including reads, writes, file creation and deletion, and so on. The file system supports multiple concurrent transactions. Thanks to a sophisticated data structure, the file system is efficient in terms of read/write-operation counts, flash-storage overhead, and RAM usage. In fact, the file system typically uses several hundreds bytes of RAM (often less than 200) and a bounded stack (or no stack), allowing it to be used on many 16-bit microcontrollers. Flash devices wear out; each block can only be erased a certain number of times. The file system manages the wear of blocks to avoid early wearing out of frequently-used blocks.