Officially, the ability to backup from one My Cloud to another will depend on the My Cloud model and the firmware it is running. Currently the second generation single bay My Cloud units running V2.x firmware DO NOT support being a backup target for another My Cloud. See the following WD Knowledgebase article that indicates which My Cloud units support being a backup target for another My Cloud device.
Unofficially it may be possible to use SSH to issue a Rsync command to copy data from one My Cloud to another. Or it may be possible to use FTP which is insecure to copy data from one My Cloud to another. Another potential unofficial option is using GoodSync.
