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 ToolCopyright (c) 2013 Microsoft Corporation. All Rights Reserved.Evaluated folder: .Evaluated folder size: 78.30 GBFiles in evaluated folder: 13Processed files: 8Processed files size: 78.30 GBOptimized files size: 13.45 GBSpace savings: 38.41 GBSpace savings percent: 74Optimized files size (no compression): 26.83 GBSpace savings (no compression): 25.03 GBSpace savings percent (no compression): 48Files excluded by policy: 5Small files (<32KB): 5Files excluded by error: 4Sharing violation: 4

More information on the tool can be found at https://technet.microsoft.com/en-us/library/hh831700.aspx. This is very useful to estimate the benefit deduplication would bring to a volume.