Which of the following methods should be used when classified or sensitive data is stored on a server?

Whole disk encryption is particularly effective for protecting classified or sensitive data stored on a server because it encrypts the entire disk where the operating system, applications, and all data reside. This means that any data written to the disk is automatically encrypted without the need for additional steps.

This comprehensive approach ensures that all information on the server is protected from unauthorized access, whether that data is actively being used or is stored in the background. With whole disk encryption, even if the physical disk is removed from the server, access to the data is effectively blocked without proper decryption credentials.

In contrast, methods such as directory encryption, file encryption, or partition encryption might not offer the same level of security as they focus on specific parts of the data ecosystem. For instance, directory encryption may only protect certain folders, while file encryption requires managing encryption protocols for each individual file. Partition encryption limits protection to a designated partition, which may not cover all sensitive data if it is spread across multiple partitions. Therefore, whole disk encryption is the best choice for ensuring comprehensive security for sensitive data on a server.