Today I've been trying to go through some photos from a few years ago that I have stored on an external USB hard drive. As I've been working on them, it seems like lightroom CC is just constantly hitting the drive. I'm just trying to simply rate my photos so I can go back through. When I started the project today, it was taking a few seconds to load each image. As I go through them, I'm maybe 75% through the 550ish photos, and each photo takes 15+ seconds to render. Furthermore, it's like lightroom is constantly hitting the hard drive doing something else. Not sure what. Eventually I will be forced to fully close lightroom and start up again. It'll take 10 or more seconds just to close down lightroom, and once it's fully closed, the hard drive is no longer being hit. So it's definitely lightroom. Anyone have any suggestions for telling lightroom to not be stupid about external drives? I'd love to get through some of these photos today.
Most likely it is building your preview cache in the background while you are browsing the images in the foreground.