@InquiringMac I have completed the upgrade today and as promised I am posting my findings.
First of all, I thought the speed of the various drives are quite interesting. (all speeds are in MB/s)
Fusion Drive
Read: 300 (average)
Write: 190 (average)
Original Apple SSD (after uncoupling the Fusion drive)
Read: 415
Write: 215
Original Apple HD (after uncoupling from the Fusion Drive)
Read: 105
Write: 105
Crucial SSD (USB 3 connected)
Read: 428
Write: 370
Crucial SSD (Internally mounted)
Read: 512
Write: 460
So the Crucial SSD is actually considerably faster than the original Apple SSD. This is quite a pleasant surprise to me.
The process I followed was as such:
- Updated my Time Machine backup as a last resort safety,
- Connected the Crucial SSD using a USB3 adaptor and formatted,
- CCC cloned my fusion drive onto the Crucial SSD (Including the recovery partition),
- Booted from the Crucial SSD (USB3 connected) to test functionality,
- Uncouple the Fusion Drive using Terminal (this also formats the two drives),
- Swap the Apple SSD with the Crucial SSD,
- Boot-up, all done.
One piece of advice. When you open up the Mini to swap the SSD, I found there is no need to unplug the Fan, nor the Wi-FI aerial. All you need to do is unscrew them and move them to one side.