Explanation

AWS Storage Gateway Volume Gateway is the correct solution because:

• iSCSI Connectivity: The Volume Gateway provides iSCSI (Internet Small Computer Systems Interface) connectivity, which allows on-premises applications to access cloud storage as if it were local block storage.

• Use Case: This is specifically designed for scenarios where on-premises applications need to connect to AWS storage using standard iSCSI protocols.

Why other options are incorrect:

• AWS Storage Gateway File Gateway: This provides file-based access (NFS/SMB protocols), not iSCSI block storage access.
• Amazon API Gateway: This is for creating, publishing, and managing APIs, not for storage connectivity.
• AWS Transit Gateway: This is a network transit hub for connecting VPCs and on-premises networks, not specifically for iSCSI storage connectivity.

The Volume Gateway comes in two modes:

1. Cached volumes - Store primary data in Amazon S3 and retain frequently accessed data locally
2. Stored volumes - Store entire dataset locally and asynchronously back up to AWS

Both modes provide iSCSI connectivity for on-premises applications to access AWS storage resources.