Development Notes - File systems - NILFS

Abstract

NILFS2 is a log-structured file system (LFS) supporting continuous snapshotting. In addition to versioning capability of the entire file system, users can even restore files mistakenly overwritten or destroyed just a few seconds ago. Since NILFS2 can keep consistency like conventional LFS, it achieves quick recovery after system crashes.

NILFS2 creates a number of checkpoints every few seconds or per synchronous write basis (unless there is no change). Users can select significant versions among continuously created checkpoints, and can change them into snapshots which will be preserved until they are changed back to checkpoints.

There is no limit on the number of snapshots until the volume gets full. Each snapshot is mountable as a read-only file system concurrently with its writable mount, and this feature is convenient for online backup.

References

[1] "the Nilfs version 1: overview" by Nilfs team (paper) [PDF]

[2] "Development of a New Log- structured File System for Linux" by Ryusuke Konishi (presentation) [PDF]

[3] "Filesystem Support for Continuous Snapshotting" by Ryusuke Konishi, Koji Sato, Yoshiji Amagai (presentation) [PDF]