A company plans to upgrade Amazon EBS volumes from gp2 to gp3 and wants to avoid any downtime or data loss on the EC2 instances during the migration. Which approach accomplishes this with the LEAST operational overhead?

Changing the volume type of an existing Amazon EBS volume from gp2 to gp3 is the most efficient method to upgrade with minimal operational overhead and no downtime. This in-place modification allows you to directly change the volume type, size, IOPS, and throughput while the volume remains attached and in use by the EC2 instance. The change propagates automatically, and performance improvements are typically realized within minutes. Creating snapshots and new volumes (option 1) or manually transferring data (option 2) involves detaching and reattaching volumes, which causes downtime and significantly increases operational complexity. AWS DataSync (option 4) is designed for large-scale data transfers between different storage services or on-premises to AWS, not for in-place EBS volume type changes, making it overkill and inefficient for this specific scenario.