It's not really affordable to upgrade the SSD since it is a 7 pin proprietary SSD and swapping the 1 TB spindisk would have me to deal with the fan issue/firmware that comes with this computer for the secondary drive. The computer has two Thunderbolts and four USB 3.0. You can use it in a fusion drive configuration, but I'm not. I have an iMac 27' i7 3.4 Ghz late 2012 with an proprietary SSD 121 GB (!) and a 1 TB seagate 7200 rpm spindrive.
