Ok I have a separate external enclosure which only offers usb and for one drive only. My iMac sees both drives when i put them one at a time in there. I have formatted them to extended journaled. I place both in this new enclosure since I need firewire 800 and 4tb. It doesn't mount or show up in disk utility. What am I doing wrong. I have tried the fw 800, fw400 and usb on this drive enclosure. I have powered off the unit and restarted my mac and still nothing. What am I doing wrong? Thanks for any help.