We have a site to site DFSR on Windows Server 2008 R2 that has been running perfectly between site A to site B until someone dumped a 20GB folder. This has overwhelmed the upload and make the internet almost useless at site A (the upload is low at the branch office).
We have removed this folder from the DFS share on site A, however the internet is still really slow.
Is there any way to cancel this sync or other way to get DFSR back in to a happy state?
Don't confuse DFS Namespaces with DFS Replication (I've edited your question to reflect this).
Replication is configured via the 'Replication' part of the DFS Management util, as shown below.
Now that you've removed the folder, have you tried restarting the DFSR service at both ends?
You might want to also consider throttling the bandwidth allocation during working to prevent this happening again, by selecting the replication group in the DFS Management tool, and clicking on 'Edit Replication Group Schedule'
