Synchronize servers on different sites

Having 2 sites, Site 2 with a low internet bandwidth. Seafile server is on Site 1.
Users on Site 2 are not able to sync all to the server.
It could be great to have 2 local Sefile servers, one on each site synchronizing between them and users synchronizing with the local server.

Doesn’t the Real-time-backup come your request near. You can try to mod this, but I think you shouldn’t get into Bandwith problems, 1GB upload should be possible today.