
ChronoSync
ChronoSync can synchronize, backup, and create bootable backups to almost anything you can connect to your Mac: select cloud services, other Macs, NAS drives, external drives, PC's or anything you can mount as a volume.
DirSync is a directory synchronisation tool, which can also be used for backupping data.
DirSync is an intuitive backup tool that can be run without installation. By comparing source and target files, only required files are copied, which greatly increases the working speed. By using multiple jobs, it is possible to perform complex data backups.
DirSync can work with drive serial number instead of drive letters.
portable file-synchronization folder-sync