Changing replica types

I have 5 NetWare 4.11 servers in a WAN (3 sites). As we are going to go to NetWare 5.1 I moved the master replica of [Root] from one server to another (at seperate sites) on Friday as this is the first server to go to 5.1.

Monday morning and the network at the site where I moved the master replica to is very slow. Obviously there is now more network traffic but I didn’t expect it to be this bad. Is it because NDS is still doing more stuff in the replica move? How long should it take (5 servers, 500 users roughly)?