This article will help you to understand about backup of Esync.
What if Network or Internet diconnected?
If nas is disconnected from network or internet stop while running profile then profile will resume from same point where it is stoped once it will find the network or internet connection .
For Eg :
For example data size is 1 GB and backup is running and lan network get disconnected at 500 MB ,so once it will get the machine in network it will resume from 500 + .