When you unmount and detach a volume from an instance, Windows flags the device location as offline. The device location remains offline after rebooting, and stopping and restarting the instance. When you restart the instance, Windows might mount one of the remaining volumes to the offline device location. This causes the volume to be unavailable in Windows. To prevent this from happening and to ensure that all volumes are attached to online device locations the next time Windows starts, perform the following steps: