Mac mini SSD

Hmmm. I don't think that's a thing, my friend.

A Fusion Drive is, as I understand it, a rotational drive (hdd) with flash memory elements built on, as a single unit.

I don't believe it a configuration of two separate storage units or types.

Someone please correct me if I'm wrong. (I was wrong once before.)😉

edit - if, however, you're looking to improve the performance of a Mac mini, an SSD alone would definitely be in improvement over any rotational storage device (hdd).

Oh, yes. The Mac mini can be had with a 2TB SSD installed.

And if you already have a mini without an SSD, you could add one in an external case connected by USB.

OWC is a popular go-to for Macintosh expansion ideas and hardware. OWC/Macsales SSD

macOS Catalina configures itself on installation to run from two separate drive volumes on you Mac.

The first Macintosh HD and on it lives the operating system files.

The second is Macintosh HD - data... this is where all the user data and files are stored.

It's a slick, secure system.

If you want to speed up your mini, install Catalina on an external SSD and use that as the boot disk, or replace your internal drive with an SSD and improve the performance that way. 👍🏽

Well, shut my mouth! Here's an interesting article...

https://www.lifewire.com/setting-up-fusion-drive-mac-2260165