Caching and Deferred Write of Metadata for Yaffs2 Flash File System

Abstract

Flash file systems are used for flash memory-based storage systems for more efficient use of flash memory. With the dramatic capacity increase of NAND flash memory, some NAND flash memory-based file systems are developed. The conventional NAND flash file systems synchronously write their metadata in the NAND flash for reliability. However, the synchronous writing of the metadata generates excessive garbage in the aspect of flash memory operations. In this paper, we present caching and deferred writing for Yaffs2 file system's metadata. The designed caching and deferred write scheme makes the aggregation and merging chance of subsequent metadata operations. By merging subsequent metadata updates in the cache, the number of written pages in the NAND flash is reduced. We implemented the proposed scheme of the metadata on Linux OS. The evaluation results showed that our proposed schemes reduced the aspects of the overall application time and the number of written pages by 5% to 40%, compared to the conventional flash file system.