Hi All, I'm after a bit of help and a steer in the right direction. I hope I'm not repeating or duplicating questions too much. I apologise if so, but there is a minefield of info out there. I hope also that this is the right place for this question. The situation: -I have a late 2011 Macbook pro, currently running El Capitan and I want to install a SSD. -I have created a USB installer which I can use if necessary. -I have a time machine back up -I intend to put my existing HDD back in for additional storage. I have done a lot of trawling the internet for instructions and different options of how to achieve what I'm wanting to do and I feel I'm almost there, but there are a few things that I'm not sure of and this is where I hope you can help. Questions I'm looking for answers to: 1) I'm thinking I would prefer to do a clean install of El Cap onto the SSD. I am comfortable with this process on its own. But I'm not clear on how best to get my apps and data onto the new install - should I: a) not do a clean install but recover my whole operating system from the time machine backup? Does this risk carrying over any issues with the current install? b) do a clean install and copy across specific data and apps and settings from time machine? Is this simple enough to do? Should I use migration assistant or time machine or something else? c) copy over some data from the existing HDD? If so what should come from here? I assume just data. This leads on to the next question also. 2) As I said, I intend to install the SSD and also keep the HDD installed for extra storage. If I have the 2 drives installed and then go ahead and install the operating system on the SSD, I will be left with 2 installed drives both with a bootable copy of El Cap on them. Can this scenario cause issues in terms of which disk the mac will boot from or can I select which one to boot from at startup? I do obviously intend to format the HDD eventually and remove the bootable OS, but I would ideally like to not do this until after the OS is installed on the SSD and up and running, just for extra peace of mind. 3) Which drive should I put in the main bay and which in the optical bay? I've read differing advice on this. I know that there is no sudden movement sensor in the optical bay so for this reason it would be better to put the SSD there but conversely I've read that the optical bay may or may not support as fast data transfer rates as the main bay. Could the SSD performance be restricted by putting it in the optical bay? Phew, that's it.....Any answers to the questions above or advice would be very much appreciated..... MacBook Pro (15-inch - late 2011), OS X El Capitan.