problems with serria 10.13.1 and RAID

im running a late 2011 mackbook pro... i pulled the CD rom drive and put in anutherhard drive and im running a RAID setup. im trying to upgrade to sierra 10.13.1 and am running into problems... I'm ok with getting rid of the raid setup, ive since bought an external backup. some gidence thru this process would really help me out ..