I am correct to have discovered the embedded raid technology II can only get so large. In other words, I have three 2TB drives configured as RAID5. The drives reach an array of almost 6TB for RAID0. However, when RAID5 is chosen the maxium size is approximately 3.8 thus wasting a good amount of free space. The unused space is in accessible as a second virtual volume the in the BIOS configuration as well as within Windows Enterprise Server 2008 R2.
It looks like I wasted $80 on the RAID upgrade module for the S5520HC motherboard.
In a RAID 5 configuration, you have total capacity of (n-1)*size_of_smallest_disk, where n is the number of your drives. Capacity of one drive is used for parity, which gives you redundancy. So in your case n=3, so you'll have total capacity of two drives, which is around 4TB.
For more information about RAID levels, see Intel® RAID Software User's Guide