The Design of New Journaling File Systems: The DualFS Case

This paper describes the foundation, design, implementation, and evaluation of DualFS, a new high-performance journaling file system which has the same consistency guarantees as traditional journaling file systems but a greater performance. DualFS places data and metadata in different devices (usually, two partitions of the same storage device) and manages them in very different ways. The metadata device is organized as a log-structured file system, whereas the data device is organized as groups. The new design allows DualFS not only to recover the consistency quickly after a system crash, but also to improve the overall file system performance. We have evaluated DualFS and we have found that it greatly reduces the total I/O time taken by the file system in most workloads as compared to other file systems (Ext2, Ext3, ReiserFS, XFS, and JFS). The work carried out has also allowed us to draw some lessons which ought to be taken into account when implementing new file systems