I have the Early 2008 model “Mac Pro 3,1” Manual here:
Step 1: Install the Drives
Here is what you will need and what I used:
Step One: Install the Drives:
Here is my starting point: I had four drives in the system, the two 500GB in bay 3 and 4 and the two 1TB in bay 1 and 2. I was running OS-X 10.8.2 (This is a must as it contains the terminal level disk utility that is used to create the Fusion Drive and make it available to the regular OS after booting.
Lay the Mac Pro over on its side and remove the side panel. This gives you access to the drive bays. I removed the drives from Bay 1 and Bay 2. These originally contained my Data Raid of the two 1TB drives. I fully intended to reinstall those and use them. (which all worked out) The 2.5” Samsung has to be put into the 3.5” holder before you mount it into the drive bay holder. See the Pictures. Then I buttoned the machine up and rebooted. For those who are paying attention I put an ASUS GTX570 a couple months back as 10.8.2 natively supports it. Yet one more speed increase for Final Cut and other CUDA/OpenCL applications!
Step 2: Setting Up the Drives As a Fusion Drive
Now go into Disk Utility and you should see the Fusion Drive you created. Format it and then to be safe, repair disk permissions.
In my case, I did not originally have a recovery partition (Bootup Raid doesn’t let you do that) so I re-downloaded Mountain Lion from the app store. When the installer runs, it asked me which disk to install on and I selected the FusionHD and let it do it's thing. During the install process, it asked to import everything from an older mac and I selected my old system residing on the two 500GB drives. A couple hours later and it was complete. Finally I removed the two original 500GB drives and put in the two 1TB drives that I had all my data on. They showed up and I was good to go.
Step 3: Use and Testing
I noticed that Photoshop, Final Cut and Motion all open much faster and respond quicker. Not bad for a 5 year old Mac.
Thanks to OWC computing for the original article. I didn’t buy my SSD from them but I just ordered 8 more gig of RAM for my old faithful Mac Pro from you.