Unibody Laptop Dual Drive not initializing?

Sadly, it sounds like your system is not able to support the HD drive you are using here in the optical bay.

Take a look at this: OWC Data Doubler. Slide down to the very bottom and read the section in Red.

The problem is within your system not the carrier it makes no difference who's you get if your system's CPU clock is 2.3GHz, 2.4GHz, 2.7GHz, or 2.8GHz. The platform controller chip in this series can't support SATA III (6.0 Gb/s) drives.

Here's the other rub! The HD bay has HD crash guard protection were as the optical drive bay does not so if you move your original Apple drive over you put it at risk in getting damaged if you bang the system.

OK, so what to do??

I would put the HD back in the original location and find a FIXED SATA II (3.0 Gb/s) SSD to put into the optical bay. You do need to be careful here as many SSD's are fixed SATA III (6.0 Gb/s). Some have auto sense technology which also won't work here either. They will be confused (acting like your HD is now) or drop down to SATA I (1.5 Gb/s) speed.

The last option which is what we went with is forgo the dual drive config and stick with a single drive setup. But instead of a traditional HD go with a hybrid! This drive is both a traditional HD and has a SSD acting as a deep cache. Then you get the benefits of both the deep storage of a HD and the faster access of a SSD.

Here is what we use: Seagate Laptop SSHD (ST1000LX001)