I am a new UnRAID user who never used any version but 7 and this just happened to me. I hadn't yet set up backup scripts for my databases (but now I will!) and the corruption happened on one I just set up a few hours ago, so not much was lost. That said, I don't know what could have caused it, because I only have a single drive in my array while I migrate data off existing disks I want to incorporate later. So it's not the multi-disk install theory. I also don't really have any other processes running because I just set things up. I am just going to delete the appdata and reinstall fresh, but will keep a fresh eye on this thread since I know it is something that is likely to keep happening.