Update – 11/11/2020: I’ve added a link here to Microsoft’s updated Server 2016 documentation that details deduplication – Understanding Data Deduplication
I just thought I’d post about this, as it’s something I’ve come up against recently, how to disable deduplication on a volume on Server 2012, 2012 R2 or 2016 and inflate the data back to it’s original form. In this example, the volume in question is E:
So let’s start with step one;
DO NOT DISABLE DEDUPLICATION ON THE VOLUME
If you disable dedup on the volume first, you simply stop new data being processed, rather than rehydrating your already deduplicated data.
So with that in mind the, step two would be to run the following command in PowerShell;
Start-DedupJob -Type Unoptimization -Volume E: -Full
When that job has completed, which you can check with the
command, you’ll then find that deduplication has been disabled on the disk. Since there’s still the garbage collection job to run, we need to rather counter-intuitively turn dedup back on for the volume with the following command
Enable-DedupVolume -Volume E:
Once this is done, the next step is to run the following command to start your garbage collection on the volume;
Start-DedupJob -Type GarbageCollection -Volume E: -Full
Finally, after that, the final step is to turn off dedup on the volume with the following command;
Disable-DedupVolume -Volume E:
And that should save you any unnecessary drama.
When all this is done, the volume will still show in some places like server manager sat at 0% deduplication rate, which is fine, as we’ve turned it off. I would guess this is just a bug, but it seems once a volume has been touched by the deduplication processes, it never goes back to a blank value for dedup rate.