I have a 27" iMac with Retina 5K display - Intel Core i5, current yosemite 10.10.4. I changed out the 1TB HDD with a 6TB. Reinstalled software, yielded 2 separate drives. MAIN GOAL: to create Fusion drive. PROBLEM: cannot unmount disk using terminal while booting from usb drive. I have found tons of instructions online, this site as well, none work. Disk utility will not unmount or erase the drive that has the recovery partition (actually on the 6tb drive, not on the apple SSD). What I need to find out is how to TOTALLY clean wipe each drive with no recovery partition, then I will be able to fuse them together and then add on a new install of Yosemite. The drives are already wiped clean of data, but still have the recovery causing the issue. I just want to Fuse the GD things together. I have watched a ton of videos and blogs that are supposed to deal with this, but so far none have worked. I've been using terminal to try to unmount and force unmount and fuse the drives. I have the same problem on 2 separate iMacs. Any help is appreciated. I have been working on this for 3 days and am getting very frustrated.
sites I've tried and their instruction failed:
https://www.ifixit.com/Story/12535/Adding_SSD_and_new_big_HD_as_Fusion_Drive_to_ iMac
http://forums.applecentral.com/ubbthreads.php/topics/625647/How_to_create_fusion _drive_und
Mac mini (Late 2012 and later), iMac (Late 2012 and later): About Fusion Drive - Apple Support
https://www.youtube.com/watch?v=oGPCQVm403M
http://www.macworld.com/article/2014011/how-to-make-your-own-fusion-drive.html
iMac with Retina 5K display, OS X Yosemite (10.10.4)
