The general consensus is that motherboard RAID is crud, put in for people who think all buzzwords were created alike. Usually it's proprietary (need to replace your motherboard? You might lose your RAID array), it's lower in performance compared to software RAID, and overall is one of those things that when it works it's okay, when it fails you'll have headaches with no end (unless you make good backups.)
Go software or with a dedicated hardware controller for RAID.
By the way-mirroring isn't a backup. You get a corrupt drive, corrupt software, deletion of something important...instant mirror! Now you have twice the corruption and still lose the file you delete. Keeping your data safe involves making backups.