iMac mid 2011, try to do fusion drive Samsung 860 EVO - error, don’t work, try to do additional driver to CD-ROM cable, sometime iMac see SSD sometimes fully missing, so i spent 2-3 days, than i thought SSD broken, check it for all test on another PC computer all work well, try again iMac - no result don’t work and all. So i have do conclusion iMac mid 2011 27 inch don’t work with new samsung 860 EVO 250GB , by the way still work my fusion drive at my old 250GB Samsung EVO 840.