Openfiler is a browser-based network storage management utility. Linux-powered, Openfiler delivers file-based Network Attached Storage (NAS) and block-based SAN in a single framework. It supports CIFS, NFS, HTTP/DAV, FTP, and iSCSI.
Very simple disk synchronization suitable for maintaining a backup directory. I built it to keep Photos and MP3s on my NAS in sync with my laptop and desktop. Will do one-way or two-way (mirrored), but does not delete. All Java, no GUI.