In accordance with one or more aspects, a storage volume is transformed into an encrypted storage volume or an unencrypted storage volume using a multi-phase process. One or more parts of the storage volume that have not yet been transformed are identified, and one or more parts of the storage volume that are allocated for use are identified. In a first phase of the multi-phase process, one or more parts of the storage volume that have not yet been transformed and that are allocated for use are transformed. In a second phase of the multi-phase process, after the first phase is finished, one or more parts of the storage volume that have not yet been transformed and are not allocated for use are transformed.