I have a 2013 13'' MBP, upgraded to 16 GB RAM. I replaced the superdrive with a Samsung 840 SSD enclosed in an optical bay. The original HDD is still in the primary drive slot. SSD is where I installed OS. HDD is where I store music, photos. EVerything works perfectly until today, I just noticed that the HDD disappeared! I tried to reconnect the HDD cable, nothing changes. I can feel that HDD is still spinning from the noise and vibration. Do you guys know what is going on here? This really freaks me out. Thanks for your help!