Which data-at-rest encryption method encrypts all data stored on the volume and all snapshots created from the volume?

The most appropriate data-at-rest encryption method that encrypts all data stored on the volume and all snapshots created from the volume is whole instance encryption. This method is designed to apply encryption to the entire instance, ensuring that all data, including that which is stored on volumes and any snapshots derived from them, is automatically encrypted without needing to individually specify what should be encrypted. This provides a comprehensive security measure, allowing for simpler management of encryption across all data associated with the instance.

Other encryption methods have more specific scopes. For example, volume encryption focuses on encrypting a specific volume rather than the whole instance, which might not automatically encrypt snapshots derived from that volume. Directory encryption targets data at a more granular level within directories instead of encompassing all data on the instance or volume. Application-level encryption is implemented at the application level, meaning that only certain data manipulated by specific applications will be encrypted, potentially leaving other data unprotected.

Whole instance encryption, therefore, offers a broader and more automated approach to securing all data within the instance framework.