Which solution would meet these requirements?
Create a snapshot of the old databases and restore the snapshot with the required storage
Create a new RDS DB instance with the required storage and move the databases from the old instances to the new instance using AWS DMS
Create a new database using native backup and restore
Create a new read replica and make it the primary by terminating the existing primary
Explanations:
While creating a snapshot of the old database allows for backup, restoring it with a smaller storage size is not supported in Amazon RDS. RDS requires that the storage size be equal to or larger than the original instance during restoration, making this option not feasible for downsizing storage.
Creating a new RDS DB instance with the required storage and migrating the databases using AWS Database Migration Service (DMS) is the best option. This allows for the downsizing of storage while minimizing downtime and impact on production, as DMS supports near real-time migration with minimal service interruption.
Using native backup and restore may involve significant downtime and manual intervention. Additionally, it requires careful handling of data consistency and integrity during the migration process, making it less ideal for maintaining operational continuity compared to other options.
Creating a new read replica and promoting it to primary requires that the original instance be available throughout the process. This may introduce complexity and potential downtime, especially if there are issues with data replication or if the transition is not seamless. It is not the most efficient method for downsizing storage.
I think the answer is:
Create a new RDS DB instance with the required storage and move the databases from the old instances to the new instance using AWS DMS