You can check out the Chinese Verison of this blog by go here: {Mac mini 2012 i7 升级256G SSD 双硬盘 Fusion Driver}

Recently, I just got a Mac mini 2012 refurbished i7 Quad Core version.  (when I say recently, I mean couple months ago.) The only performance bottle neck is the HardDrive just been too slow. (1TB HDD). Since the Mac mini 2012 is supporting dual-drive, Figure out upgrade two dual drive with the combinational of SSD. Apple so called, Fusion Drive.

I was following this YouTube Link:  Video Tutorial

Here is the list of Stuff you will need:

SSD:
 I got a Crucial M550 256G Version when it was on sale for $89.99
Crucial M550 Product Page    Amazon Link: Crucial M550 — Amazon

Mac mini Dual-Drive Kit:
I got it from eBay for $15.99
Here is the link:  Mac mini Dual-Drive Kit

Tool Set:
I got it from homeDepot for $3.88
Here is the link: Tool Set

Total Cost:  $109.86
Total Hour: 2 Hrs