I am using a maxed-out mini 2012 with dual SSD in RAID 0. Never had an upgrade problem until High Sierra, hoped they would solve the issue in Mojave but apparently no such luck - "You may not install to this volume because it is part of an AppleRAID". I understand it might be possible to install Mojave from an external boot drive, but apparently I will run into the same problem with any future updates. Any solutions?