An Efficient Metadata Index Structure for Flash File Systems

SUMMARY One way to use NAND flash memory as storage media is a flash file system. In order to design a high-performance flash file system , designing an efficient index structure that constitutes the locations of metadata including directories and files in flash memory is important. For large-capacity storage, the index structure must be stored in the flash memory to achieve low memory consumption , but this may aggravate system performance. In this paper, we propose hybrid indexing scheme to reduce the recur-sive flash updates as well as inode embedding scheme to minimize additional flash writes. We implemented a prototype called Direct Flash File System (DFFS) in a Linux OS with kernel version 2.6.21 on an embedded device. Comprehensive evaluation results using Postmark and Filebench show that DFFS has not only comparable performance to JFFS2 and YAFFS2, but also better performance than UBIFS while achieving a small memory footprint and instant mount time.