Storage Gateway: Your On-Prem to Cloud Translator

WHY IT EXISTS: Applications built for on-premise data centers expect to communicate with storage using established protocols like NFS (file) or iSCSI (block). Cloud storage, however, uses modern web APIs like REST. Rewriting legacy applications to use these new APIs is often expensive or impossible. Storage gateways were created to solve this impedance mismatch.

THE MENTAL MODEL: Think of a storage gateway as a universal adapter for your data infrastructure. It sits in your local data center and presents cloud storage to your servers in a format they already understand—a local file share or a block storage volume. Your servers interact with the gateway, and the gateway handles the translation and transmission to the cloud behind the scenes.

HOW IT WORKS: A storage gateway, implemented as a hardware appliance or a virtual machine, resides on your local network. It translates traditional storage protocols (like NFS, SMB, iSCSI) into cloud-native API calls (like REST). When an on-premise application writes a file, the gateway receives it, translates the request into a cloud API call (e.g., a REST PUT), and sends the data to the cloud storage service. It often includes local caching to improve performance.

WHEN TO USE IT: Use a storage gateway for hybrid cloud scenarios where you want to connect existing on-premise systems to the cloud. This is ideal for backing up local data to the cloud, implementing a cloud-based disaster recovery strategy, or tiering infrequently accessed data from expensive local storage to cheaper cloud object storage without re-architecting applications.

WHEN NOT TO USE IT: Avoid using a storage gateway for high-performance, latency-sensitive applications. The round-trip time to the cloud will always introduce latency that a purely local storage array doesn't have. It is not a replacement for a high-speed local SAN for a primary production database.

ONE CANONICAL EXAMPLE: A company's backup software is configured to write to an on-premise server via the iSCSI protocol. To save costs, they want to store these backups in the cloud. They deploy a software-based storage gateway. The backup software now targets the gateway as its iSCSI device. The gateway receives the block-level data, converts it into objects, and uploads them to a cloud storage bucket, all without changing the backup software's configuration.