To SSD or not to SSD?

Replacing the HDD with a large SSD is a good option, however I do not think that fusing SSDs would be any better than just running one large SSD or running macOS on one and storing data on the other. .

IMHO the single large SSD option, is better because it is easier to setup, maintain, troubleshoot, update and backup.....

FWIW I have a couple of upgraded Late 2012 Mac Mini's, one with dual SSDs and one with a single large SSD. The one with dual SSDs used to be a little faster with the SSDs in RAID mirroring, until APFS busted Raid setups. Today both are running strong with read/write speeds at around 480/520 MB/s.

I agree with @den.thed about not using a Fusion drive if you can afford a 2TB SSD. Whether you keep the original SSD installed for extra storage is up to you.

Just make sure to have good verified working backups since SSDs can fail without any warning. Recovering data from an SSD is difficult to impossible.

Steve Burke wrote:

Forgot to mention that I'll primarily be working on very large image files in Photoshop.

You need all the RAM that you can stuff in the Mini since Photoshop is

such a memory pig. Also, depending on what you mean by "very large",

the max 16GB RAM of the 2012 Mini may not be enough. Then there is

also the issue of the integrated graphics. Many Photoshop actions and plugins

leverage the GPU.

My personal experience with PS and integrated graphics and Minis is

that PS works, but you will be waiting a lot of the time, especially

with "very large" files.

Steve Burke wrote:

If I wanted to remove the Fusion drive SSD, replace it with a 2Tb SSD and keep the 1Tb spinning HD (as an additional separate internal drive) rather than remove both OE drives and replace them both with the one 2Tb drive

It's totally up to you which combinations of drives you choose. Also keep in mind, that the original HDD and SSD will preform just as fast in external USB 3.0 enclosure's as the did internally.

Right here, I would like to add that both my Mac Mini's run much cooler and quieter without an HDD churning inside them.

how easy is it to ‘un-fusion’ the system so it thinks I have 2 separate drives rather than one ‘fusion’ drive.

Make a good backup using Time Machine and/or CCC. Get the 2T drive setup and running first. Then erase and re-format each of the original drives as separate drives. At this point, it will not matter if one is internal or both are in external exclosures.

I've googled how to separate the drives and i believe that i have to do that in Terminal.

Yes, it's very easy to un-fuse a Fusion Drive within Terminal using an external boot. Not knowing what OS is on the Mini, you should be able to boot into Internet Recovery (Command+Option+R) or from a USB thumb drive with an OS installer on it then use Terminal commands as you found via Google. I have done it many times and it's very easy.

Also, I agree with your thinking to simply replace the current SSD with a 2TB SSD and leave the 1TB HDD alone. Extra storage!

I agree with other users: I'd go with the 2TB SSD.

size of system memory would also have a say in terms of large photo work