Chris
I am sure it is a PERC H310 Adapter RAID Controller , that came with the system, or may be a PERC H710 Adapter RAID Controller, 512MB NV Cache. I can't remember what was ordered. it was only about 6 weeks ago. The system was set up by Dell when it was ordered. It only needed to be finalized when we received it.
I don't remember seeing the array as offline when I looked.
I am sure it is to do with the active partition, as that was the only thing I did before it would not boot.
Hope this helps.
Trevor