Q: I have enabled data deduplication on a Windows Server 2012 volume, so why is nothing happening?

A:The data deduplication role doesn't start data deduplication immediately. It will try to run in the background when the system is fairly idle and at thetimes specified in the schedule when data deduplication was configured.

To force an optimization pass to start, use the Start-DedupJob Windows PowerShellcmdlet, passing the name of the volume on which to start the optimization.

The Start-DedupJob command below would start the optimization on the D drive (note thatdepending on the size of the volume, this job could take many hours to complete):

PS C:> Start-DedupJob D: -Type Optimization

It will return input similar to this:

Type ScheduleType StartTime Progress State Volume

---- ------------ --------- -------- ----- ------

Optimization Manual 0 % Queued D:

To check on the status of the running job, use this PowerShell cmdlet:

PS C:> Get-DedupJob

It returns input such as this:

Type ScheduleType StartTime Progress State Volume

---- ------------ --------- -------- ----- ------

Optimization Scheduled 0 % Queued D:

Optimization Scheduled 0 % Queued D:

Optimization Manual 4:38 PM 24 % Running D:

If you find the deduplication jobs are stopping very quickly, you might not have sufficient free memory available. Normally you should ensure there is atleast 1GB of free memory when running the disk deduplication optimize job. Check the Applications and Services, Microsoft, Windows, Deduplication,Diagnostic event log if you are experiencing problems.

To find the details on the deduplication status use this PowerShell cmdlet

Get-DedupStatus

outputting in list format to get the maximum detail:

Volume : D:
VolumeId : \?Volume{284a417e-6457-11e1-b9e1-001517c4e105}
Capacity : 1.82 TB
FreeSpace : 803.84 GB
UsedSpace : 1.03 TB
SavedSpace : 216.33 GB
SavingsRate : 70 %
OptimizedFilesCount : 17442
OptimizedFilesSize : 307.63 GB
InPolicyFilesCount : 42112
InPolicyFilesSize : 1.22 TB
LastOptimizationTime : 4/9/2012 3:45:05 PM
LastOptimizationResult : 0x00000000
LastGarbageCollectionTime :
LastGarbageCollectionResult :
LastScrubbingTime :
LastScrubbingResult :

The results above reflect the state of my D volume: Only 24 percent through the optimize process, and it's already deduplicated over 200GB of data.
 

To see more answers about Windows Server 2012, Windows 8, virtualization, and all things IT,  click over to our FAQs page.