Why is a thick provisioned ONTAP LUN larger than its parent volume?

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Category:: ontap-9

Specialty:: core

Last Updated:

Applies to

ONTAP 9

Answer

This is expected behavior when the following environmental conditions are met:

A space-reserved LUN in a volume with a space guarantee of VOLUME
The fractional reserve on the volume is set to 0
The volume has storage efficiency features (deduplication) enabled
The LUN has space reservation honored = false

Additional Information

To check Space Reservation and Space Reservation Honored please run the following command:

cluster1::> lun show -vserver vs1 -path /vol/vol1/lun1 -instance
              Vserver Name: vs1
                  LUN Path: /vol/vol1/lun1
               Volume Name: vol1
                Qtree Name: ""
                  LUN Name: lun1
                  LUN Size: 10MB
                   OS Type: linux
         Space Reservation: enabled
             Serial Number: xxxxxxxx
       Serial Number (Hex): xxxxxxxx
                   Comment: new comment
Space Reservations Honored: false
 ...

For more information regarding NetApp's best practice for LUN configuration please review, What is the proper configuration for a volume containing a LUN?

There is a current request for enhancement with our Engineering team to prevent this issue in future ONTAP releases.