Ext3cow is an open-source, versioning file system based on ext3. It provides a time-shifting interface that allows a real-time and continuous view of the past. This allows users to access their file system as it appeared at any point in time.
Some advantages of ext3cow:
1.
• It does not pollute the name space with named versions
2.
• It has low storage and performance overhead
3.
• It is totally modular, requiring no changes to kernel or VFS interfaces
http://www.ext3cow.com/