Which storage class is most suitable for backups of data that will be stored for two years and is unlikely to be accessed?

The Archive storage class is specifically designed for long-term data storage with infrequent access. Given that the data will be stored for two years and is unlikely to be accessed during that time, Archive offers the most cost-effective solution. This class is optimized for data that is rarely needed but still must be retained for compliance, regulatory, or backup purposes.

In contrast, the Standard class is intended for frequently accessed data, which would not be economical for storing backups that are not intended for regular access. Nearline is better suited for data that is accessed less than once a month, making it inappropriate for data expected to be untouched for two years. Coldline is tailored for data that may be accessed less frequently than once a year, offering lower costs compared to Nearline but still involves slightly higher retrieval fees than Archive.

Therefore, for backups that will remain untouched for an extended period, Archive is the ideal choice due to its lower storage costs and suitability for rarely accessed data.