That's pretty much the only thing I can't decide on! As I recently got more into photography with the purchase of an Olympus OMD EM5, I plan on installing and using Lightroom on my new iMac. This will be my first installing Lightroom on any of my computera, so I am not very familiar with the program, though I have read up on it (the catalog system, etc..) and have seen it in action before. Ideally, I would probably go with the 3TB Fusion since the price difference is not too bad compared to the 1TB and I wouldn't need an external for a while, but on the other hand I don't want to hamper myself in the event I need to install Bootcamp to run certain software for work. As you know, currently Bootcamp is NOT possible on the 3TB. This has me leaning toward the 1TB Fusion. If I go with the 1TB (install Lightroom and put the catalog file on the 1TB) and use an external drive to store my photos, would I lose speed/performance compared to if I had all the Lightroom program, the catalog file and all of the photos on the same 1TB? I want Lightroom to run/load as smoothly as possible. Could you recommend a good external for this particular purpose? Any help would be appreciated, especially with folks that are familiar with Lightroom. Thanks much!