the VSA is a virtual storage appliance, it will take the local disks that are assigned to it and offer them out to other hosts as a DataStore. it will replicate data, but only between Hosts in the VSA pooled storage, not between disks on a single host.
vSphere does not support Software RAID at all, the only way to get a RAID of disks is to have a hardware RAID controller, check out the HCL and remember eBay is your friend.
From your posts I am making the assumption that this is a lab environment not a production server, there for optimal performance is not necessary so get yourself a second hand one from ebay.