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How NTFS Deduplication Works

NTFS data deduplication is functionality that is included with Windows Server 2012 operating systems. NTFS data deduplication removes duplicate data from a volume, which in turn lets you store more data on the volume.

NTFS data deduplication should not be confused with Arcserve Backup data deduplication. NTFS data deduplication is Windows implementation that affects the data that resides on a volume. Arcserve Backup lets you back up and restore data that resides in NTFS data deduplication enabled volumes. Arcserve Backup data deduplication is an implementation that affects how backup data is stored on storage media. For more information about the Arcserve Backup implementation of data deduplication, see the section Using Deduplication. For more information about NTFS data deduplication, see the Microsoft Windows Development Center website.

You define NTFS data deduplication as a local backup option or as a global backup option.

The process of backing up NTFS data deduplication data is the same as the process for performing any other type of standard backup to disk or to tape media. This approach also applies to restoring data that was optimized by NTFS data deduplication. However, when you restore data that was backed up as optimized NTFS data deduplication, there must be a sufficient amount of free disk space on the destination volume that is greater than or equal to the logical size of the files that you want to restore.

Example: File A is 100 MB and file B is 100 MB. Both files contain the exact same data. With an optimized NTFS data deduplication backup, the storage space that you require is 100 MB. However, to recover both files, you require 200 MB of free disk space on the destination volume.

Note: This example does not apply to recovering data using Arcserve Backup disaster recovery operations.

With NTFS data deduplication you can perform optimized backups and non-optimized backups, given that NTFS data deduplication is enabled on the volume that you are backing up. With optimized backups, Arcserve Backup backs up the optimized files, the non-optimized files, and the chunk store. When you perform optimized NTFS data deduplication backups but NTFS data deduplication is not enabled on the volume, Arcserve Backup performs optimized backups.

The following limitations apply to NTFS data deduplication backups:

• By default, the optimize NTFS data deduplication option is enabled as a global backup option and disabled as a local backup option. With this configuration, Arcserve Backup performs optimized backups on all NTFS deduplication enabled volumes.

  To enable or disable this option for backup jobs for specific volumes, disable this option as a global backup option and then enable or disable (as appropriate) as a local backup option.

• Arcserve Backup can recover data from optimized backup sessions to only computers running Windows Server 2012.
• With NTFS data deduplication backups, Arcserve Backup backs up only the data deduplication settings. For example, the Enable data deduplication, Deduplicate files older than (in days), and File extensions to exclude options. For all other options, (for example, the Set Deduplication Schedule settings) Arcserve does not include the settings with full volume backups because it cannot restore the settings with full volume restores. When you want to recover all of the deduplication settings, you must recover the entire computer or perform a disaster recovery of the computer.
• Arcserve Backup cannot perform Compare jobs on data that was backed up using the NTFS data deduplication (optimize) option. When you submit Compare jobs of this type, the jobs fail and an error indicating as such (Compare job not supported) appears in the Activity Log.
• When you perform optimized NTFS data deduplication backups and specify the Compare Backup Media to Disk option, Arcserve Backup compares only the reparsed files (not the entire volume).