I know in times past that installing the Mac OS from scratch had a habit of creating a 'fusion' drive if you had both a SSD and HDD in the same box and this could create some odd disk errors down the line.

I currently have Catalina (10.15.7) on a Late 2012 Mac Mini with two SSDs in it (250Gb + 1Tb SSD) and I could really do with more space. I could go out and buy a new SSD but tin drives are still cheaper (£70 vs £160 for 2TB) and as this is for archive and music files speedy access is not needed on this drive. Also the 250Gb drive is a full dismantle (again) so I really only want to do it once more on this Mac. Next time it becomes a 4Tb NAS box :-)

I've seen odd posts about 'core storage' and have a Mac that Disk Utils will not run due to 'core storage' issues but cannot see a simple (ha-ha) explanation of the AFPS / Core Storage file types and its been 3 O/S versions since I messed with multiple types of disk.

I also know you used to be able to 'un-Fusion' a drive with diskutil resetFusion and going by this support entry I think it sill exists but it seams daft to have it created and then destroy it (time if nothing else).

So two bits of advice please:

  1. Is there is a way to avoid the old 'fusion' issue on a clean Catalina install with a SSD and HDD in a Mac Mini?
  2. Where can I find details on Apples newer storage as DuckDuckGo fails me?
  • If I recall correctly you have to purposefully set up a Fusion Drive, it is not automatic and can't be set up accidentally. Just format the drive(s) normally and point the installer to the drive you want the OS on. – Steve Chambers Oct 13 at 23:53

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