Chosen Solution

Dear all, my FusionDrive in my 27” iMac (Late 2015 IIRC) died, it briefly spins up and then down again, then the circle with line icon shows. Any attempt to fix this failed, so I am going to replace the drive. I ordered this kit here: https://eustore.ifixit.com/products/imac… without an SSD as I think I’ll go for a conventional HDD such as the WD Red editions I have running without issues in my NAS for years. 1.) Can I use any hard drive, or does the drive need a specific spec like regarding transfer rate? 2.) What is the HDD enclosure with USB in cable in the kit for? Many thanks & best regards, Robin Update (01/25/2021) Hello Dan Many thanks for your answer. Let me give some more detail. The 3TB Fusion Drive crashed on me and I do not want to go back to a fusion drive as I think it was a good solution back in the days were SSDs were expensive but today I think it’s a flawed design because there is no longer the need to have two systems (SSD and HDD) working together and sharing blocks of the same file. I do not want to fix my Fusion drive. I first wanted to sell the iMac as I bought a new iMac already. I therefore planned on putting a 500GB SSD in it. But I now have changed my mind and will keep the iMac for my man’s cave. I don’t need the speed of an SSD for that, so I therefore rather put a conventional WD Red CMR enterprise disk in it. So therefore more questions:

  1. Can I use any 3.5” drive or is there some spec they need to specifically have? I have this one in mind.
  2. Can I use the adapter cable that came with the kit? I suspect yes and stick the temp sensor near the center IIRC as in the manual on this site
  3. I still wonder what that iFixit black enclosure with USB cable is for? Many thanks and best regards, Robin

Hold on here! Why are you jumping to a 2.5” drive Vs sticking with the 3.5” your system uses? If you are going to go with a HDD then stick with a 3.5” as they run at a faster RPM (faster) Frankly, I would go with a hybrid SSHD drive which is a even better than a HDD. But we still have the SSD drive mate of your current Fusion Drive to deal with. How about telling us a bit more on what you use your system for so we aim you to the best option for your needs. Update (01/25/2021) To help clarify a few points you raised in your update… 1 - The WD Red drive don’t offer same caching as the traditional drives as its intended for NAS systems which you don’t want caching as that can screw things up in a RAID set which is what most NAS’s are setup with. 2 - You don’t need an external thermal sensor in your system if you are running the newer firmware (newer macOS release). So the only things you would use here is the tapes and the tools. 3 - The external 2.5 case was so you could connect your new SSD to your system to allow you to use TimeMachine and Migration Assistant to install a fresh OS and copy-off your user accounts, apps and data over. You do want to reformat your blade SSD fully so it doesn’t get used as a caching drive.