Seems both "Storage Gateway – Volume gateway stored volumes" and "DataSync" are able to backup data from on-premises to S3 asynchronously. What are the difference between Storage Gateway – Volume gateway stored mode vs. DataSync? And what are the scenario for both functions?
Both are similar in their functions, but I would say DataSync is more flexible as it can be used to sync with EFS or FSx in addition to S3. It is a stand-alone VM that connects to your existing NFS volumes and manages a sync to AWS storage resources.
Storage Gateway Volume Gateway can be thought of as a pseudo-NAS itself that syncs to S3. You can attach to its volumes via iSCSI on the Storage Gateway itself, which are synced to S3.
Subtle differences but similar use-cases.