ENFFiS: An Enhanced NAND Flash Memory File System for Mobile Embedded Multimedia System

Abstract

Since the typical erase cycle limit of a NAND flash memory's block is about 1,000,000, flash memory should be erased as evenly as possible; otherwise, file system hot spots will soon be worn out. This forces a NAND flash memory file system to scan the whole flash memory during its mount rather than saving frequently updated file system information in a fixed area. Since the mount time linearly increases with the size of NAND flash memory, boot times of embedded systems are also linearly increased. In addition, since data loss may occur if a file system terminates abnormally due to unexpected errors, a stability scheme for NAND flash memory file system is in great demand. To resolve these problems, this article suggests an extended logical block called Exblock (Extended Block) and a table called SNode (Snapshot Node) to reduce the mount time and proposes a new journaling scheme to improve stability for an enhanced file system for NAND flash memory storage called ENFFiS (Enhanced NAND Flash memory File System). It also proposes a new cache policy to improve read/write performances. ENFFiS shows better performance than existing file systems in terms of reading, writing, mount time and stability.