The solution requires on-premises block-based storage where all data is available locally, with backups sent to AWS. AWS Storage Gateway's Volume Gateway in "stored volumes" mode is designed for this exact scenario. It presents iSCSI block volumes to on-premises applications, satisfying the block storage requirement. With stored volumes, the entire dataset is maintained on-premises for low-latency access, meeting the local availability requirement. The gateway then asynchronously creates point-in-time snapshots of this data and stores them in Amazon S3, fulfilling the AWS backup goal.

A. Amazon S3 is an object storage service. The backup application requires block-based storage and cannot write directly to the S3 API.

B. Amazon S3 Glacier is an object-based archival storage class. It does not provide the required block-based storage interface for the application.

C. Gateway-cached volumes store the primary data in Amazon S3 and only cache frequently accessed data locally, which violates the requirement that all data must be available locally.

1. AWS Storage Gateway User Guide

"How Volume Gateway works": This section explicitly details the two modes. For Stored volumes

it states

"If you need low-latency access to your entire dataset

first configure your on-premises gateway to store all your data locally. Then

asynchronously back up point-in-time snapshots of this data to Amazon S3." This directly aligns with the question's requirements.

2. AWS Storage Gateway User Guide

"Stored volumes": This page further clarifies

"Stored volumes store your primary data locally

while asynchronously backing up that data to AWS... Stored volumes provide your on-premises applications with low-latency access to their entire datasets."

3. AWS Storage Gateway User Guide

"Cached volumes": In contrast

this page explains

"Cached volumes let you use Amazon S3 as your primary data storage while retaining frequently accessed data locally in your storage gateway." This confirms why it is the incorrect choice for the scenario.