File Defragmentation Scheme for a Log-Structured File System

In recent years, many researchers have focused on log-structured file systems (LFS), because it gracefully enhances the random write performance and efficiently resolves the consistency issue. However, the write policy of LFS can cause a file fragmentation problem, which degrades sequential read performance of the file system. In this paper, we analyze the relationship between file fragmentation and the sequential read performance, considering the characteristics of underlying storage devices. We also propose a novel file defragmentation scheme on LFS to effectively address the file fragmentation problem. Our scheme reorders the valid data blocks belonging to a victim segment based on the inode numbers during the cleaning process of LFS. In our experiments, our scheme eliminates file fragmentation by up to 98.5% when compared with traditional LFS.