Rsync is one of the best backup software tool. It was originally designed to replace rcp, the vulnerable old Unix remote copy program. Because of its sophisticated means of synchronizing and transferring files and directories, rsync is widely used for mirroring Web sites. rsync transfers only the changes in files, using the devilishly clever rsync algorithm. It calculates difference without needing both files to be present. Rsync greatly improves efficiency when compared to traditional remote backup methods. By synchronizing only those files that have changed since the last backup, using rsync results in large bandwidth savings.