I have an iPhone 4S that downloaded iOS 9 the other day. Now I lost a ton of storage. I went to Settings > General > Usage > Manage Storage, selected Delete Update, and selected Delete Update again to confirm - but the file was relatively small. Where did the rest of my space go?
I've deleted old apps and moved most photos off the phone, no music or videos. In the usage folder, the thing taking up the largest space is photos at only 266 MB. In fact, I added all the apps together and it's only 1500 MB (around 1.5 GB) Where did it all go? 6 GB max storage.