I have an airport extreme to which I connect to wirelessly, connected to one is a hard disk, it has a usb hub on the disk enclosure and another hard disk is piggy backed on this. My question is I open both disks in finder and copy files on one disk to the other (they are large files 200GB). Does the traffic travel from one disk wireless to the mac then wirelessly back to the router to the other disk, or does the traffic travel straight from one disk to the other direct by USB. The write times are long!! Should I connect both drives to the mac to copy the large files?