Neste caso em particular (suponho que seja o mesmo com todos os provedores de IaaS), é possível anexar um volume existente a uma instância diferente.
De documentos oficiais da Amazon
Prerequisites
- Determine the device names that you'll use. For more information, see Device Naming on Linux Instances.
- Determine how many volumes you can attach to your instance. For more information, see Instance Volume Limits.
- If a volume is encrypted, it can only be attached to an instance that supports Amazon EBS encryption. For more information, see Supported Instance Types.
- If a volume has an AWS Marketplace product code:
- The volume can only be attached to a stopped instance.
- You must be subscribed to the AWS Marketplace code that is on the volume.
- The configuration (instance type, operating system) of the instance must support that specific AWS Marketplace code. For example, you cannot take a volume from a Windows instance and attach it to a Linux instance.
- AWS Marketplace product codes are copied from the volume to the instance.
Depois disso, é o mesmo procedimento que qualquer servidor físico.