KevinS
Senior Insider
iOS 10.3 introduces a new file system. You cannot roll back from iOS 10.3 to a previous iOS version. You can wipe your iDevice and restore from backup, but only if you have a good backup available. Do a backup before you install iOS 10.3.
http://bgr.com/2017/03/30/ios-10-3-features-list-apple-file-system-warning/
http://bgr.com/2017/03/30/ios-10-3-features-list-apple-file-system-warning/