Over the weekend I did the daring deed and opened up the 2014 mac mini and replaced the mechanical HDD with a OCZ Vertex 4 SSD. I was having some issues cloning the drive (appears due to lack of support of SATA III on my USB-SATA controller?) so I went ahead and swapped the drives anyway and installed a fresh copy of Yosemite on the SSD. I then used the migration assistant (in the installer) to port over the Yosemite information from the HDD. Unplugged the HDD from the USB port and made sure to select the SSD as the startup disk in the System Preferences. Everything runs fine and quickly, but occasionally theres a little snafu when it boots. When it boots, a good number of the time there's a grey folder with a ? inside, indicating it doesn't know what to boot from. From there, two different scenarios have occurred 1. Boot, grey screen with folder and ?. Plugged in the yosemite boot drive I made, nothing happens. Power down the machine, reboot it, and it goes into Yosemite just fine. 2. Boot, grey screen with folder and ?. Plugged in the yosemite boot drive I made, it begins to load the Yosemite installation. Once into the installation screen, I went into into startup disk and chose the SSD, restarted, and it boots fine. It goes back and forth between the two, anyone know why this happens and what I can do to remedy it? I've already gone through and verified/repaired the disk/partitions and the permissions. Any other ideas?