Design & Implementation Of Ext2 Snapshot On Linux

Snapshot is a photography terminology, which freezes the image at a particular time. Its key technology is copy-on-write mechanism. When snapshot is used to take a picture on file system, it can create a "freeze frame" of the file system. Once a snapshot has been taken, subsequent changes to the file system do not overwrite the freeze frame at the time of snapshot. They will be written to the other locations in the same file system. This idea can be used to backup the total file system in a very short time period. It is not necessary to have additional disk space to save data while doing backup. Additional disk space is only required when files and directories are actually modified later. The Ext2 FileSystem supports the strong expansibility. The detailed process of design of Ext2ss has been divided into four parts on the whole: realization of Disk format, realization of directory file snapshot , realization of the snap creation in the ioctl, realization of Copy-on-write of mechanism. The snapshot based on Ext2 can help the Linux's users to backup and recovery the data.