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Check how much space will be saved using Windows deduplication feature

Q. How can I check how much space I will save if I use data deduplication in Windows Server 2012 and above?

A. Microsoft provide a tool, DDPEval.exe, which when used will provide a break down of the savings that will be had if data deduplication is used. The tool can be used against a file share, a driver or a specific folder. Below is an example execution and pay attention to the Optimized files size and space savings details:

PS D:\> ddpeval .
Data Deduplication Savings Evaluation Tool
Copyright (c) 2013 Microsoft Corporation. All Rights Reserved.

Evaluated folder: .
Evaluated folder size: 78.30 GB
Files in evaluated folder: 13

Processed files: 8
Processed files size: 78.30 GB
Optimized files size: 13.45 GB
Space savings: 38.41 GB
Space savings percent: 74

Optimized files size (no compression): 26.83 GB
Space savings (no compression): 25.03 GB
Space savings percent (no compression): 48

Files excluded by policy: 5
Small files (<32KB): 5
Files excluded by error: 4
Sharing violation: 4

More information on the tool can be found at This is very useful to estimate the benefit deduplication would bring to a volume.

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