What is the MOST cost-effective way to make storage available to the company’s legacy backup system?

Explanations:

Launching an Amazon EC2 instance with Amazon EBS volumes is an expensive and complex solution. EC2 instances and EBS volumes would require ongoing costs, and setting up a VPN for connectivity introduces additional complexity. This is not the most cost-effective approach for integrating legacy backup systems with cloud storage.

Shipping backup tapes to AWS for storage in Availability Zones is not a practical or cost-effective solution for regular data backups. This option would introduce delays, logistical issues, and would not provide real-time backup capabilities. It is not suited for continuous or timely data backup needs.

Using AWS Snowball to transfer data on a weekly basis to Amazon Glacier involves physical shipment of devices, which adds operational overhead. Snowball is typically for large, one-time data transfers and not for ongoing, regular backup processes. Additionally, Glacier retrieval times may not meet the needs of frequent backup systems.

AWS Storage Gateway with a Virtual Tape Library (VTL) using iSCSI is specifically designed to integrate with legacy backup systems. It allows the legacy backup software to write to cloud storage as if it were a local tape device, without the need for significant changes to the existing backup system. This is the most cost-effective way to extend legacy systems to cloud storage.