Using an elevated command prompt ( right click, run as Administrator ) execute the following:
C:\Users\ryv> dfsrdiag.exe backlog /SendingMember:ServerX /ReceivingMember:ServerZ /RGName:RepGroup /RFName:"Data"
So what does this do? The initial part of the command is dfsrdiag.exe - the program to run the diagnosis. The switches are as follows:
/SendingMember:ServerX - this is the server pushing data to the replication partner
/ReceivingMember:ServerZ - and this is the server receiving the data
/RGName:RepGroup - DFS Management has servers in groups so it will want the group name
/RFName:"Data" - DFS is capable of managing different folder groups with different sync settings so you have to specify the folder.
If all is going well the result from this command should come back with something like:
No backlog - member <ServerZ> is in sync with partner <ServerX>
If it doesn't come back with this then the fun begins. Once I have a good example I'll post that.