BE15 backup DFSR performance very low

Dear, we are in China, we are using BE 15 running on windows 2012R2 physics server, flash installed, we have a server on VM platform 5.1, this server have a drive attached from a NAS volume, this drive set the DFS replication with another server in Europe, backup the data on this drive directly the performance is OK, but backup the DFSR is very slow, sometimes 100MB, sometimes 50,20, ever 2MB, i guess the problem maybe is the DFSR setting, have any way to speed up? thanks