So, before I do iMac surgery, I need to figure out whether I need a?¡°stick¡± SSD or a ¡°drive¡± size SSD to replace my Fusion drive. I think?there¡¯s a way to reformat the SSD portion of the Fusion drive and leave?it in the case, but I suspect if I want the fastest performance I want the?SSD ¡°stick¡± to insert on the motherboard in the same place, in which the?SSD part of the Fusion drive becomes useless silicon, and perhaps the?rotating platter becomes a second internal drive.
Jim Robertson
I *think* Apple implementation is that there are a physically separate?¡°blade¡± SSD and a SATA rotating disk HD which are *electronically*?merged to act like a single fused drive.
iFixit¡¯s site shows your model with a blade SSD and also with a HDD.
If you replaced the HDD with a SATA SSD (e.g.,?an?OWC Mercury Extreme?Pro 6G) in 1- or 2-TB size,?I don¡¯t know how you would tell?the OS to NOT try to make it a fusion drive.
Or maybe, while you¡¯re in there, you also replace the small blade SSD with a not-quite-so-small super-fast SSD, and let the 2 be a fusion pair.
Jim Saklad