If you attempt a dynamic disk group split or join command when a volume is in use, Storage Foundation puts up a message asking whether you want to force the split or join. If the volume is in use because it is selected in Windows Explorer, then you can force the split or join safely. However, if the volume is in use within an application, it is not recommended that you attempt to complete the command. If a volume is regenerating, resynching, or recovering, then even if you force the split or join, the operation is not successful.