Will Apogee Duet conflict with Firewire external hard drive?


I've just ordered an Apogee Duet, but wondered if will conflict with the Western Digital hard drive I've got connected to the second Firewire port on my 2008 iMac (with its single Firewire bus). I once had an M-Audio Solo which constantly lost its connection when the WD drive was active, but I've heard that some audio interfaces and external HDs can coexist happily.

I've got the option to attach the WD drive to a USB port, but would prefer to keep it on the FW port if possible.

Can anyone comment please?

Thanks George, I should have made clear that the iMac does have two FW ports sharing the same bus, so it looks like I'll be OK.