Issues with Samsung SSD's!

Hi, i have same issue, Beware iMac 27 mid 2011, don't work with samsung 860 EVO (Because samsung use unsupported new controller) Also same situation can be with 850 EVO (I didn't check with this series), so optimal for upgrade without any risk will be use 840 EVO series. Symptomatic is next: When you connect 860 EVO (I check it) or 850 EVO (I didn't check it 850 EVO, so info for 850 EVO maybe not correct).

You can start from internet recovery but you cannot do fusion drive, for fusion drive you should start from USB recovery, yes you can do fusion drive with 860 EVO or 850 EVO but then when will be recovery from time machine you will se error and time machine is stop, then if you will try install new system to you new fusion formatted disk, you will cannot install, not sierra, not sierra high, maybe el captain will work but you will see many error when install it (6 hours maybe), if you still install some OS don't start to be happy, because will be many errors and white screen.

So by the way. If you try to instal os to pure ssd, it's also will be with error. So conclusion don't use 860 EVO and 850 EVO with iMac 27 mid 2011 (I have core i5 3,1). So your SSD will work with USB 2.0 on your iMac, or need to buy thunderbolt ssd adapter or thunderbolt usb 3.0