(An) efficient flash file system based on the metadata management, writeback, and duplicate elimination for nAND flash memory storage systems

Abstract

Flash memory has become an increasingly important component as a nonvolatile storage media because of its small size, shock resistance, and low power consumption. In nonvolatile memories, NOR flash memory provides fast random access speed, but high cost and low density, compared with NAND flash memory. NAND Flash has advantages in large storage capacity and relatively high performance for large read and write in contrast to NOR flash. Currently, due to its physical characteristics, block level translation interface, called flash translation layer, is required between an existing regular file system and the flash memory chips. However, the approach of regular file systems, which is mounted on top of the emulated block level interface, has many restrictions and is inefficient because these file systems are designed for the disk based storage device. There were some approaches that file system directly uses flash memory without intermediate interface, called flash file system. The popular flash file systems include Journalling Flash File System and Yet Another Flash File System. However, they have many restrictions in their architectures, thus show poor performance in booting time, garbage collection overhead, and memory footprint. In addition, another serious problem in flash file systems is very poor write performance. In this dissertation, an efficient flash file system is proposed and designed for NAND flash memory storage. The proposed flash file system considers both issues the regular file system and flash memory. Target performance metrics are the system booting time, memory footprint, and garbage collection overhead, which are important issues in flash memory. First, the proposed flash file system tried to store the whole data index entries within inode structire in order to reduce the flash scan time. For this, each inode occupies a whole flash page to preserve sufficient available indexing space. In addition, it provide two inode classes: one has a...