Disabling Data Deduplication on Windows Server 2012R2


Sometimes you have to give up a technology because it doesn’t suit all scenarios….

Today, I had to remove Windows Server 2012R2 Data De-duplication, which is a very clever technology that reduces disk space use.   The downside in my scenario was that it also seemed to cause massive slowdown in Windows Server Backup, and whilst it gave me great disk space savings (60%) it meant having to close down Hyper V instances.   I sure hope that Microsoft in Windows 10 Server give us better usage of De-duplication on live HyperV guest systems, and not just VDI instances.

Anyway…   the point of this post is more for my own future reference, as well as maybe helping someone else out there who is removing Data De-duplication from Server 2012 R2.


Disabling Data De-duplication doesn’t “undupe” the data already “duped”.

If you disable Data DeDuplication via the GUI or Powershell, it does not actually undo the work it has done.   Worse, if you have disabled, you also cannot run a garbage cleanup command (which cleans up the data created by the deduplication technology).

So, its important that you leave Data Deduplication enabled, but EXCLUDE the entire drive first.   Then, run the following two commands (which will take ages to run dependant on the amount of data you have).


The unoptimise command:

start-dedupjob -Volume <VolumeLetter> -Type Unoptimization


Check the status:



Clean up the Garbage:

start-dedupjob -Volume <VolumeLetter> -Type GarbageCollection


Check the status:



Once you have both of the above done, and it will take a while, you can remove the deduplication role from your server.