I have recently made this upgrade to my Macbook Pro and I even consulted the Genius at the applestore for advice. They were very helpful and recommended placing the SSD in place of the hard drive location and if you wanted to keep your hard drive, then to put it in place of the optical drive using the Opti Bay Enclosure. The Genius was telling me there is a difference in speed depending on which of the two locations you put it in. It was a significant difference but I cannot recall off the top of my head the figures. Over all, he recommended installing the SSD in place of your current hard drive. A faster read/write speed will not compensate for placing it in the optical bay drive. Hope this was of use to you! The SSD is a very impressive upgrade and I wish you the best of luck.