I went ahead and attempted to add a 500GB 7200RPM WD Scorpio (Black) to the second, unoccupied port on my 2.5Ghz Discreet i5. I'm pleased to report that it is possible to add a second hard drive to your non-server (2011) Mac Minis. Many thanks to saulinpa for pointing out the appropriate part number from the 2010 server model! For anyone who's familiar with the 2011 mini teardown, this install should only take about 15 minutes, view instructions on the teardown at iFixit, also further notes on an SSD upgrade. Otherwise, the process was as follows, apologies for the dark photography, I didn't feel like post-processing photos today... (*IMPORTANT* footnotes at the end): Disclaimer: this upgrade will most-likely void the manufacturer warranty on your mini as going beyond upgrading RAM is not recommended/supported by Apple documentation. Complete this at your own risk. (7/31/11) I ordered the "Bottom Hard Drive Flex Cable" (part: 922-9560) from macpartsonline.com. They have them for a steep $33 and even steeper $16 shipping charge. Hopefully iFixit or another company will be able to manufacture/reproduce the part for significantly cheaper. Otherwise, shipping was speedy (it made it from LA to NYC in 2 days) Testing out whether the cable fits, and it does! Then fitting the cable and my SSD into the extra port. It might be a little difficult to make out, but you can see in the second photo that the new cable matches up nicely to the second SATA port. Adding the new hard drive and snapping in the cables. Nice!! Started up, and my mini is 500GB healthier! Important Footnotes: I did make a couple faults, nothing major, and definitely/likely a reflection of my overeagerness and intermediate level of computer knowledge, but definitely for your consideration. During the teardown, you'll need to slide the motherboard out of the case at least 1/2 inch. The iFixit teardown demonstrates this, though they neglect to mention that you should remove the motherboard mounting screw underneath the fan. I also suggest that you disconnect the power supply cable on the right of motherboard, just behind the RAM slots. DO NOT SWITCH YOUR ORIGINAL HARD DRIVE TO THE SECOND PORT: I had neglected to buy Hard Drive mounting screws for the new HDD, and figuring that the SSD doesn't require as secure a seating, I decided to transfer the existing mounting screws. Ultimately, this made me believe that the original drive (the SSD with Lion installed) would work perfectly fine in the additional port. WRONG! Booting up after the first upgrade attempt, the mini took about 30 extra seconds searching for the bootable drive, then was excruciatingly slow starting various applications. I tried setting the "Startup Disk" in System Preferences to no avail. So I ended up having to do the upgrade all over, moving the SSD back to the original port. After I did this, the mini was back to its speedy self! If you decide to seat the original HDD/SSD in the additional SATA port, a fresh Lion re-install will likely be required. Luckily, the mounting screws on the HDD fit perfectly into the mounting holes for the extra drive. I'll go ahead and get another set of mounting screws soon. I have a Crucial M4 SSD, which is physically larger than the HDD, which makes for a very tight fit if the SSD is going to be seated in the original port. Be sure to check the drive's cable's connection before you close the mac mini back up! That's about it for me. This write seriously took 3-4 times as long as the upgrade. Hopefully we'll see more mini owners taking advantage of that second port. Such a money saver and an elegant solution if you have the resourcefulness!