Cloud Storage Gateway (CSG) is a gateway service that can be deployed at your data center or on Alibaba Cloud. CSG uses Object Storage Service (OSS) buckets as backend storage devices. CSG provides on-premises and cloud applications with standard file services over the Network File System (NFS) and Server Message Block (SMB) protocols. CSG also provides on-premises and cloud applications with block storage services over the Internet Small Computer Systems Interface (iSCSI) protocol.

CSG supports two types of gateways:

  • File gateways

    File gateways use OSS buckets as backend storage devices, and map the object directory structure of OSS buckets to NAS file systems. You can read and write all objects in a specified OSS bucket over standard NFS and SMB protocols. CSG also uses on-premises storage to cache hot data, and provides high-performance data access in addition to the large storage capacity of OSS buckets. File gateways are compatible with the Portable Operating System Interface (POSIX) and third-party backup software. If you want to back up small files or share small files for reading and writing, we recommend that you use file gateways of the Standard or Basic type. If you have high performance requirements or want to use multiple clients to simultaneously access shared data, we recommend that you use enhanced or advanced types of file gateways.

  • Block gateways

    Block gateways create storage volumes in OSS and allow you to access OSS by using the iSCSI protocol. On-premises applications can access these volumes as iSCSI targets. Block gateways run in two modes: pass-through and cache. In the pass-through mode, data in iSCSI volumes is sliced and synchronized to the cloud. This mode is applicable when you use high-speed links such as Express Connect circuits. In cache mode, you can create on-premises cache disks to accelerate read and write operations, and transfer data to the cloud in an asynchronous manner. This mode is applicable when you require efficient access to on-premises cached data but have an average performance for uploading data to OSS.


You can use cloud gateways and on-premises gateways to build a storage gateway cluster. Then, you can share data between the cloud and your data center. This allows you to migrate data in various business scenarios, such as file backup, data distribution, and disaster recovery. You can also use the clusters to distribute data to multiple data centers.

CSG is a lightweight storage gateway, which can be deployed at your data center and on Alibaba Cloud.


  • File gateways
    • Build a file storage service for a large file system when local storage is limited.
    • Store data as objects in the cloud, and allow applications to access the data in a file system without the need to modify code.
    • Access shares in a file storage service among multiple data centers.
  • Block gateways
    • Back up data to the cloud by using backup software that supports efficient data transfer over iSCSI.
    • Import video streams to storage volumes over iSCSI to store data in the cloud.