I still love the ix4-200d NAS, but there are a few things that got left out of the owner's manual that I had to figure out by trial and error.

1. Rsync only works against unsecured (wide open public) folders.
2. If you need secured folders to keep your vital files from being accidentally moved/touched/altered/deleted, using CIFS sharing will enable the security, but you may find that file copy or sync operations take longer than just an rsync operation due to additional overhead in the protocol. SMB signaling can get loused up quickly on a slow or unreliable link.
3. If you absolutely need to move large files between two of these at geographically distant locations, you can set up an rsync or copy operation to a USB-attached hard drive, mail that drive to the other location and rsync them from the drive to the destination folder. A poor-man's workaround for keeping fulls and incrementals in sync when the line just won't pass enough traffic to suit.
4. Turn off the power saving on the hard disks. Nice idea, but it takes almost a minute to spin all of the drives up so that the share becomes usable. Unless you really love watching the Windows hourglass spin...