Microsoft Dedup

Posted by robd on September 22, 2018
Server 2012

I posted about Microsoft Dedup recently and thought I should mention how to setup dedupe:

Data deduplication is a feature that allows space reduction on a data volume by removing duplicate copy of data and replacing it with a reference file that looks exactly the same to the end user.

Microsoft does not recommend dedup on databases such as .edb, .mdf and .ldf files. This feature help IT admins reduce storage costs if it’s applied to the right data such as File shares such as home folders.

Below is the recommendation of dedup feature based on data type

Recommend Deduplication File Servers, VHD Files, Software Repositories, Backups and other static data.
Not Recommended Virtualization Hosts, WSUS, Database servers or any data that changes very frequently.


  • Windows Server 2012 Operating system
  • At least 4GB of RAM
  • 1 CPU core and 350MB of RAM for every 1.5TB worth of data
  • Must be on non-system volume such as boot volume
  • Mapped drives via net use is not supported. Must be a local volume.
  • Must be using NTFS with MBR or GPT partition
  • Not supported on ReFS file system

To install the deduplication feature, use the Server Manager – Server Manager > Server Roles > File and storage services > File services > Data Deduplication.

Or PowerShell

Run below powershell commands to install the feature
Import-Module ServerManager

Add-WindowsFeature -name FS-Data-Deduplication
Import-Module Deduplication
To turn on deduplication feature, use below command (where E is the volume)
Enable-DedupVolume E:
To Set the minimum file age before deduplication
Set-Dedupvolume E: -MinimumFileAgeDays 30
To get a list of deduped volumes, run
To get dedup status, run
To start a dedup job manually, run
Start-DedupJob E: -Type Optimization
To get current dedup schedule, run

How to calculate dedup rate

Installing the “Data Deduplication” feature will automatically install the DDPEVAL.exe in c:\windows\system32 . This tool will allow you determine if deduplication is effective your data type.

This tool can be copied from any server running Windows Server 2012 R2 or Windows Server 2012 to systems running Windows Server 2012, Windows Server 2008 R2, or Windows 7. You can use it to determine the expected savings that you would get if deduplication is enabled on a particular volume.

To use:

DPEval <VolumePath:>

C:\> DDPEVAL.EXE \\Server\Testshare

More info:


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