A Cloud Storage Gateway is a software or hardware networking device located at the customer premises that translates cloud storage APIs like - SAOP (Simple Object Access Protocol) or REST (Representational State Transfer) to block-based storage protocols like - Fibre Channel or iSCSI or file-based interfaces like - NFS or SMB.
Also called as a cloud storage controller or cloud storage appliance, a cloud storage gateway establishes simple connectivity to allow the incompatible technologies to communicate transparently. The gateway can make cloud storage emerge as a block storage array, backup target, NAS filer or even an extension of the application itself.
A cloud storage gateway can be a stand-alone computing device or a virtual machine that bridges cloud storage systems and enterprise applications.The need for an interface between them arose because of an incompatibility between the protocols used for public cloud technologies and legacy storage systems. A majority of public cloud providers rely on Internet protocols, usually a RESTful API over HTTP, rather than conventional SAN (Storage Area Network) or NAS (Network-attached Storage) protocols.