If you want to make life more difficult for yourself by going RAID in a WHS, do it in hardware so WHS is oblivious to the fact. However, it's meant to *not* use raid, and it's not JBOD--underneath the user exposed system it is quite aware of multiple drives, and depending on your folder duplication choices it will keep your data spread on multiple, standard NTFS formatted drives.
Your best bet would be getting some external drives, using them to backup the WHS, and keeping them offsite. And optionally use some of the cloud storage systems as well for further redundancy/convenience factor.