“Apple sells the Fusion drive as a $799 option with the new Mac Mini and iMac,” MacTuts+ reports. “In this tutorial we will look at building and creating our own Fusion Drive for much cheaper rates that gives the same performance as Apple’s Fusion Drive.”
To create a Fusion Drive, you will need three sets of storage drives:
• A hard drive
• An external drive to backup to – creating a Fusion volume will erase both the SSD and the hard drive, so if you have information on the hard drive you want to keep, you’ll need to have a copy of that data elsewhere. This is optional and if you are just setting up your mac you wouldn’t be needing an extra drive to backup to.
• An SSD installed/to install. It is possible to build a Fusion Drive through an internal or externally connectedd SSD. Though the recommended method is using an internal drive because if you accidentally remove the SSD – the Fusion Drive would not function and will crash. In this tutorial we will be looking at building a Fusion Drive through an internally connected SSD. Nonetheless, the process and commands are the same for an externally connected SSD, so you can always follow these steps.
Full tutorial here.