Hi, I use a lot removable storage. Be it pendrive or ssd for Virtual Machine. I need to force myself to remember to call sync. I do wonder if it's possible for dolphin to handle itself. Adding some animation would make it clear.
This should be done in KIO so I'll move this there. syncfs or fsync is what we need to use here IMO. I think the solution with the least disadvantages is calling "syncfs()" once on any removable data storage once a copy job is fully completed, and only then reporting the copy as finished. If that isn't enough, we might need to fsync every file once.