RN528X drives constantly spinning even after a reboot, what is causing this?!

Was the OneDrive Personal sync, which I learned a bit about. First, the Settings/Options portion is set to automatically sync every 30 seconds. Since my OneDrive Personal isn't changing all THAT fast, I would expect this to maybe burp briefly every30 seconds. But no, it just grinds continuously at this setting. I changed it to once/day and now it's nice and quiet like it should be. Another thing I noticed is the default sync is bi-directional - however since OneDrive Personal files are all stored in the cloud, the only real purpose of the NAS drive's copy is a back-up in the event I cancel OneDrive or whatever. And it's basically just another back-up that I can locally fetch if need-be. OneDrive has been rock solid for years (we use it in Corporate as well) so it's probably a waste of time to even have this app running at all. But anyway, thanks very much for yours and Sandshark 's suggestions. As usual you guys helped me get to the bottom of a nagging problem.