Recently my old fusion drive (1T HHD + 128G SSD) on my 2012 late Mac mini might have issues. The OS is very slow and has some read errors when I tried to use CCC to clone it. Anyways, I managed to copy some necessary files to another external drive and am trying to replace this fusion drive with one 2TB SSD and do a clean install. Do I need to split the fusion drive before I take them out of Macmini if I want to use them as two separate external drives later or I could just remove them without the split and format them later as two external drives? Thanks.

  • If you got read errors when copying, you're better off restoring from your backup to the new disk.
    – benwiggy
    Commented Jul 27, 2020 at 12:28

2 Answers 2


You can remove them without any fuss or erase. Fusion is a software layer, not something that changes on the hardware side.

You can remove and erase / format them in any order you like. If you haven’t formatted then yet, maybe try that unless you’re sure you want an SSD even if they work, but I’m guessing you know they still work since you plan on reusing them.


I had a 2012 Mini with a Fusion drive, and I swapped out the SSD for much larger SSD. (I didn't have the courage to remove the mechanical drive, which requires 'extra steps'.

As soon as you remove one of the drives , then that breaks the Fusion scheme.

When I rebooted, the mechanical drive was reported as an 'Unknown Format', and needed to be partitioned. (Given its age, I only used it for temporary storage of things like installers that I could always download again.)

  • Thanks. My new SSD to be installed is 2TB already. I thought 2012 Late Mac mini could only support up to 2TB. I knew it is quite a hassle to remove the 1TB HD (upper bay). Do I have any other options?
    – Richie
    Commented Jul 27, 2020 at 12:55
  • I don't think that's true: I'd certainly want some evidence either way. But youve already bought the 2TB unit, so go ahead with that. Replacing the internal SSD with a larger one made it so much faster.
    – benwiggy
    Commented Jul 27, 2020 at 13:05
  • In this old thread (discussions.apple.com/thread/7083401), somebody said the limit is 2TB. But I have no other evidence so far. I will replace the 128GB SSD with the new 2TB SSD for sure but am not sure whether I should leave the 1TB HD installed or not.
    – Richie
    Commented Jul 27, 2020 at 13:16
  • They're saying that the largest size you can buy in 2015 is 2TB. They're not saying there's a physical limitation that prevents it coping with more than 2TB of storage. Yes, just leave the HDD in. It won't slow you down. As said, I left it in mine.
    – benwiggy
    Commented Jul 27, 2020 at 13:20
  • OK. Thanks for the heads up. If I will leave the HDD in. So two new questions: Do need to split the fusion drive before installing the new 2TB SSD? And the old fusion drive has read errors when I backed up files as mentioned earlier. I am not sure theses errors cam from HDD or SSD. If the HDD has issues, do I need to fix it first?
    – Richie
    Commented Jul 27, 2020 at 13:32

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