Yes it's a different type of RAId that doesn't share really the same name but yet is still considered. It's called JBOD ( Just a Bunch of Disks) You can together add different disks of different sizes if needed to make one giant drive operating at the speed of the slowest disk. I'm not sure how you can tell if it's supported but it was in my P65PT Deluxe manual that I have in RAID arrays.
here is a wiki article on it.
Standard RAID levels - Wikipedia, the free encyclopedia
I believe that is what you need however I thought RAID 0 would work for what you need...