I'm looking for a soloution to backup two 2TB drives with another two 2TB drives in raid 1 for a media server. If I can do this I'd also like to know if I can use another single drive (no raid)for the OS.
Any backup or cloning software will do that.
Windows sees a RAID drive as a single drive.
Paragon is excellent software for this purpose.
Clonezilla is excellent free software, if you can understand it.
You can mix RAID drives with single drive in the system.