The story of DFS and one-way replication

Greetings. Finally my schedule allows me to blog a little bit again, and this time I’m going to return to DFS Replication (DFS-R) and mention a few things about one-way replication.

The default

A default DFS-R setup features a two-way replication which replicates all changes made in either enabled partner in the replication group. This means that any changes made on any partner will be replicated throughout the replication group. Now there are several scenarios (for example software distribution from a central storage) where you want to prevent changes made in the branch offices to replicate.

One-way replication vs Read-only replication

With Windows 2008 R2 we got the option to make replicated member read-only. This marks the entire replicated folder, with subfolders and files, as read only for all users. This way there is no replication from this member because no changes can ever be made. This is the supported way of achieving one-way replication, but you are limited to read access and can’t make any changes whatsoever to the replicated folder.

 

DFS-R_readonly

 

The other way is to manually edit the replication connections and set the connection status to “disabled”. This will prompt a warning message saying the topology is not fully connected. This configuration is NOT supported but it kind of works. So what does “kind of works” mean? Well, say there’s a central site and a branch office with DFS-R to replicate a folder and you disable the sending connection from the branc hoffice to the central site.

  • Files and folders created in the central site is replicated to the branch office
  • Files and folders created in the branch office are not replicated to the central site

So far so good? However:

  • If a file is first copied to the branch office, and later an updated version of the same file is copied to the central site, the older version in the branch office will not be updated.
  • This seem to be true for Windows Server 2008 R2 and in my Windows 2012 lab, the file in the branch office is replaced and local changes are being discarded when a newer version of that file is copied into the central site.
  • I have not found anything that suggest this configuration is supported in Windows Server 2012

DFS-R_oneway

 

To sum up

The choice of one-way replication in DFS-R is to make a replicated member real-only if you are using 2008 R2. This is the supported configuration. There are an unsupported way which is to disable the replication connections in DFS-R and it works with one exception unless you run Windows Server 2012 where so far this seem to work as it should.

 

I hope you have enjoyed this post, more DFS-R to come so stay tuned 😉