[Hampshire] DIY RAID - quick answer required

Hi all

In preparation for my DIY DROBO project, I'm fiddling about with RAID but I have a quick question as I'm short of time. Can someone please give me a yes/no answer to this (assuming it is that simple a question)??

Is it possible to setup RAID (RAID 1 I think is what I'm after i.e. same data gets sent to 2 separate drives simultaneously) across two drives where one is internal PATA IDE (and indeed this wil be the drive the system boots from) and one is external USB?

The reason I ask is if, for example, what I'm proposing is impossible - I need to pop out this afternoon and get another external USB HDD - which I won't have time for over the weekend.

Cheers - sorry the question's a bit garbled I am very short of time.
Rob