Efficient Metadata Management for Flash File Systems

NAND flash memory becomes one of the most popular storage for portable embedded systems. Although many flash-aware file systems, such as JFFS2 and YAFFS2, were proposed, the large memory consumption and the long mount delay have been serious obstacles for large-capacity NAND flash memory. In this paper, we present a new flash-aware file system called DFFS (direct flash file system) which fetches only the needed metadata on demand from flash memory. In addition, DFFS employs two novel metadata management schemes, inode embedding scheme and hybrid inode indexing scheme, to improve the performance of metadata operations. Comprehensive evaluation results using microbench- mark, postmark, and Linux kernel compilation trace, show that DFFS has comparable performance to JFFS2 and YAFFS2, while achieving a small memory footprint and instant mount time.