iomega ultramax plus 4TB Hard Drive

So I've just purchased this Iomega Ultramax plus 4TB Hard Drive. It has 2x2TB hard drives in it's enclosure. I have set the physical switch on the back of the drive to Raid 1. So first part complete.

The whole purpose for me is that I have redundancy. So I'm not wanting to partition the drives any further. I just want 2 identical 2TB drives working as mirrored. Now, in disk utility, it shows up as one 2TB hard drive. So far so good. But the question is, where do I go from there? Do I still need to partition this hard drive? Do I pick '1 partition' instead of 'current' which is what it is showing by default. or do I still pick 2 partitions or do I do nothing at all. Help? Thank you.