Data Deduplication and BackupAssist

Microsoft Windows Server 2012 R1/R2 includes a technology called Data Deduplication, which reduces the amount of disk space taken up by your data. Let’s take a deeper look at what Deduplication means for you and how this technology relates to BackupAssist.

Deduplication is lot more efficient than Single Instance Store or NTFS compression, because it can remove duplication of data within a file. Microsoft has found that enabling deduplication provides gains of up to 50% on file shares and 90% for VHD libraries.

How does deduplication work?

Windows Server Data Deduplication segments files into dynamic chunks (32kb-128kb) and then identifies the duplicate chunks. One copy of each duplicated chunk is maintained and compressed, and retrieved by files as required. Redundant copies of critical and popular chunks are also retained to protect against the impact of data corruption.

For more information on how Windows Server Data Deduplication works, see this MSDN article.

How is deduplication enabled?

Windows Server 2012 Data Deduplication is added as a Server Role in the Add Roles and Features Wizard, under File And Storage Services. Once you select Data Deduplication, you can install the role and then use Server Manager to select the volume that you want to enable deduplication on.

For more information on enabling deduplication on Windows Server see this TechNet article.

What can be deduplicated?

Windows Server deduplication was designed to reduce the space taken up by infrequently used data. Frequently used data and databases are skipped by the deduplication process, but the type of data that can be deduplicated depends on the version of Windows Server.

Windows Server 2012 R1

Windows Server 2012 R1 supports deduplication on NTFS data volumes. It does not support the deduplication of boot drives, system drives, CSV volumes, live VMs or databases such as SQL and Exchange.

Windows Server 2012 R2

Windows Server R2 has seen deduplication support extended to include open and active files, CSV volumes and live VHDs – in certain conditions – as explained in this TechNet article

How do you back up a deduplicated volume?

BackupAssist can back up a deduplicated volume, but maintaining the data in a deduplicated state depends on the type of backup you perform.

• A System Protection backup of a full volume maintains the data’s deduplication, and the data retains the optimized storage at the backup destination.
• A System Protection backup of selected folders or applications does not retain the deduplication and the backed up data will take up more disk space that it took up at its source.
• When selected data in a deduplicated System Protection backup (full volume) is restored, the deduplication is lost. The data will therefore take up more space when it is restored.
• File Protection and File Archiving backups do not retain deduplication and the backed up data will take up more disk space that it took up at its source.
• To retain deduplication when restoring a full volume System Protection backup, use the Windows Restore tool, or use RecoverAssist to perform a bare-metal recovery.

As noted in the points above, when deduplication is lost there is an impact on the space taken up by the data.

• For backups, this means the data will take up more space on the backup destination than it did on the data source.
• For restores, this means the data will require more space when it is restored. For example, if you have a 100mb file on a deduplicated volume, and you restore that file from an non-deduplicated backup, it may take up 150mb when it is restored.

To learn more about Windows Server 2012 Data Deduplication, see this blog article by the Program Manager of the Microsoft Windows File Server team.

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