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What's New in Data Deduplication in Windows Server 2012 R2

Published: November 1, 2013

Updated: November 1, 2013

Applies To: Windows Server 2012 R2

This topic describes features that were added to Data Deduplication in Windows Server 2012 R2, including support for optimization of live VHDs for Virtual Desktop Infrastructure (VDI) workloads.

Introduced in Windows Server 2012, Data Deduplication involves finding and removing duplication within data without compromising its fidelity or integrity. The goal is to store more data in less space by segmenting files into small variable-sized chunks (32–128 KB), identifying duplicate chunks, and maintaining a single copy of each chunk. Redundant copies of the chunk are replaced by a reference to the single copy. The chunks are compressed and then organized into special container files in the System Volume Information folder.

For more information, see Data Deduplication Overview. For recommended usage scenarios, see Plan to Deploy Data Deduplication.

The following table describes the changes in Data Deduplication functionality in Windows Server 2012 R2.


Feature/functionality New or updated? Description

Data deduplication for remote storage of Virtual Desktop Infrastructure (VDI) workloads


Optimize active virtual hard disks (VHDs) for Virtual Desktop Infrastructure (VDI) workloads by implementing Data Deduplication on Cluster Shared Volumes (CSVs).

Expand an optimized file on its original path.


Use the new Expand-DedupFile cmdlet in Windows PowerShell to expand optimized files on a specified path on the original path if needed for compatibility with applications, performance, or other requirements.

In Windows Server 2012 R2, Data Deduplication can be installed on a scale-out file share and used to optimize live virtual hard disks (VHDs) for Virtual Desktop Infrastructure (VDI) workloads.

What value does this change add?

By optimizing CSV volumes for your VDI workloads, you can stretch the virtual machine capacity of your existing storage subsystem. Storage savings as great as 95 percent can be achieved by implementing Data Deduplication on live VHDs for VDI deployments.

In Windows Server 2012 R2, the performance of VHDs optimized through Data Deduplication is fully tested and supported only on VDI workloads. The same performance gains are not guaranteed for non-VDI workloads running on Hyper-V virtual machines; nor does Microsoft offer support for these scenarios in Windows Server 2012 R2.

The space savings from data deduplication make it feasible to deploy solid system-drive (SSD)-based volumes, with their improved I/O, for VDI and to simplify supporting infrastructure such as just-a-bunch-of-disks (JBOD) enclosures, cooling, and power.

By consolidating files, data deduplication can improve caching efficiency and, as a result, I/O on the storage subsystem for some types of operation.

For more information about the benefits of using data deduplication with VDI workloads, see Extending Data Deduplication to new workloads in Windows Server 2012 R2.

What works differently?

This feature is implemented through the new HyperV usage type for the Enable-DedupVolume cmdlet, which can perform optimization on active VHD files. To enable the use of scale-out file shares for VDI workloads, data deduplication of Cluster Shared Volume (CSV) volumes is supported.

Improvements in write efficiency and faster optimization speeds were implemented to make optimization on active VHD files feasible. However, when Data Deduplication involves virtualization, the computer on which data deduplication is enabled cannot be the same server that runs Hyper-V. This ensures that optimization does not compete with the virtual machines for resources on the Hyper-V host operating system. For more information, see Enable-DedupVolume.

Your Hyper-V and VDI infrastructure can remain the same, with one exception: all VHD files for the virtual machines must be stored on a file server running Windows Server 2012 R2. The storage on that file server can be directly attached disks, such as JBOD enclosures used with Storage Spaces, or can be provided by a SAN or iSCSI storage device. To help ensure high availability of the storage, it is recommended that you use a clustered file server with CSVs providing storage for the VHDs. For procedures that describe how to set up Data Deduplication for a VHD workload, see Deploying Data Deduplication for VDI storage in Windows Server 2012 R2.

The new Windows PowerShell cmdlet Expand-DataDedupFile enables you to expand optimized files on a specified path if needed for application compatibility, performance, or other requirements. The files are expanded on the original path. For more information, see Expand-DedupFile.

What value does this change add?

This gives you a way to expand individual files within an optimized volume if for any reason the optimized files are resulting in compatibility or performance issues.

What works differently?

The capability is new in Windows Server 2012 R2.

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