The most immediate practical challenge in integrating on-premises infrastructure with AWS cloud is storage. Legacy systems read and write data using traditional protocols like NFS, SMB, iSCSI, and tape drives. The core role of AWS Storage Gateway is to enable these systems to silently use cloud storage (S3, Glacier) in the background without modification. Storage Gateway transparently converts on-premises application writes into S3 objects, EBS snapshots, and Glacier archives. Today we deeply understand the internal workings of each of the 4 types of gateways, their caching mechanisms, and usage scenarios.