Raid is used for prevention of data loss from hard drive failure. It is not a means of backup. If your raid array data was corrupted, there is no mechanism to restore it. If a raid drive dies, it will still operate while you replace it without data loss.
Raid can be implemented in hardware or software. One is not "better" than the other. Generally, hardware raid is faster though, as a hardware raid controller has dedicated hardware to do the necessary parity creation and checking to offload from the main processor in your system.
In either a hardware or software Raid scenario, you will probably have to reformat the drives that are included in the array first. Hardware raid would be the most expensive way for you to go. Windows 8 has software raid built in (storage pools) that is very effective and much better than WHS.
Please invest in a backup solution as well. Try Crashplan for a good one at low cost.