2.25. Creating a New Volume
You can add more data disk volumes to a guest VM at any time, up to the limits of your storage capacity. Both CloudStack administrators and users can add volumes to VM instances. When you create a new volume, it is stored as an entity in CloudStack, but the actual storage resources are not allocated on the physical storage device until you attach the volume. This optimization allows the CloudStack to provision the volume nearest to the guest that will use it when the first attachment is made.