FreeFileSync is a folder comparison and synchronization software that creates and manages backup copies of all your important files. Instead of copying every file every time, FreeFileSync determines the differences between a source and a target folder and transfers only the minimum amount of data needed.

FreeFileSync is a free, open source folder comparison and synchronization software for Windows, Linux and Mac OS X. It also works on 64bit operating systems on all platforms. The program can be installed in two versions: as a standard installer on Windows or as a portable application (no registry entries). Powered by a clean, easy, intuitive interface, this tool offers a myriad of features for synchronization purposes.

Features
Detect moved and renamed files and folders
Copy locked files (Volume Shadow Copy Service)
Detect conflicts and propagate deletions
Binary file comparison
Full support for Symbolic Links
Automate sync as a batch job
Process multiple folder pairs
Comprehensive and detailed error reporting
Copy NTFS extended attributes (compressed, encrypted, sparse)
Copy NTFS security permissions
Support long path names > 260 characters
Fail-safe file copy