Abstract: A cloud gateway (GW) device receives a first request for incremental backup from a client device over a LAN, where the first request includes a first file representing a difference between the incremental backup in view of a prior backup. In response, the cloud GW identifies a first base backup previously backed up to a cloud storage server over a WAN. A second request is transmitted to the cloud storage server over the WAN to copy the first base backup into a second base backup. A third request is transmitted to the cloud storage server over the WAN to replace a second file within the second base backup. The third request includes a second backup ID, a descriptor describing the file to be replaced, and content of the file received from the client without modifying the first file.