I plan on replacing my failed HDD portion of my Fusion drive inside my iMac 27, its a late 2014 model I believe. Is the HDD an Apple proprietary model or can I simply order any SATA 3.5" HDD from online and replace it with? And is it possible to have 2 physical volumes instead of one (Fusion). I would like to install the main OS onto the 128GB Flash and then have the HD as a 2nd physical volume. It makes data recovery easier if things ever go wrong.