Apple's newest storage option for the Mac is known as a Fusion drive. It effectively combines an SSD and a platter-based hard drive into what the Mac OS sees as a single volume. In addition, the OS manages the Fusion drive to ensure that data you use often is stored on the faster of the two drives, and data you use only occasionally is stored on the slower of the drives.
With a Fusion drive, you don't have to worry about managing where you store your data; the OS will take care of it for you. The only downside is that Fusion drives, at least at the moment, are a build-to-order option on the newest Mac minis and the not-yet-released iMacs. That makes many Mac users who already installed SSDs a bit sad.
But fear not. You don't need to buy a new Mac to get a Fusion drive. With a little bit of time and a bit of tinkering with Terminal, you can create your own Fusion drive.
You do need to tread a little carefully, though. The process requires erasing the two drives that will make up the Fusion drive, so be sure to create a current backup of all of your data before you begin. It's also easy to make a typo when you enter a drive name in Terminal, and end up erasing the wrong drive.
If you're ready to create your own Fusion drive, this guide will show you how: