DFS Replication is Not Compatible with NTS Deduplication

[Marc__K]

The documentation claims that data deduplication is compatible with DFS Replication, but that is not correct.  I have several systems with both enabled, some Windows Server 2012 R2 and some Windows Server 2019 systems.  If a user interacts with a file that has been deduplicated, such as moving it from one folder to another, DFS-R may log a 4406 error (The DFS Replication service encountered an unsupported reparse point in a replicated folder. This reparse point will not be replicated because the replication of this type of reparse point is not supported by the DFS Replication service.) and delete the file from the partner. 

Data deduplication uses reparse points and DFS Replication doesn't like them.  I thought that since the documentation says both technologies are compatible that DFS Replication would have been updated to work correctly with reparse points when they are related to data deduplication.

[#2]

Hello,
Did you encounter the issue with 2012 R2 specifically, or with both OSes ?

[#3]

It's occurring with both OSes. This morning a 2012 R2 system generated 2 new 4406 events. Yesterday, I "unoptimized" everything on a 2019 server and then re-enabled deduplication. That server generated a few 4406 events right after the deduplication was re-applied.

[#4]

So...This appears to have stopped after installation of the March 2023 CU on the servers. Perhaps development already had a bug logged and happened to fix it. I know I had been troubleshooting this for a while before I posted this.

[#5 · Accepted solution]

It turns out the March 2023 CU didn't have anything to do with this.  Not previously mentioned is that the systems experiencing this problem have Veeam Agent for Windows (VAW) installed.  After recently updating VAW to a newer release, the 4406 events returned.  The last time the reboot from installing the March 2023 CU must have been what actually fixed things.  This time I did a reboot without installing any additional Windows updates and the 4406 events stopped again.