If you are using a supported instance type, you can use Elastic Volumes to dynamically modify the size, performance, and volume type of your Amazon EBS volumes without detaching them. If you cannot use Elastic Volumes but you need to modify the root (boot) volume, you must stop the instance, modify the volume, and then restart the instance.
EBSのボリュームタイプやボリュームサイズなどを変更するときは再起動もデタッチもいらないが、ルートボリュームを別なEBSに変更するときは再起動が必要っぽい…
