Not reclaiming space at the volume level.

[TheX]

Data Ontap 9.1 - FCoE to Cisco UCS - VMWare 6.7

I have some volumes that are exhibiting strange behavior. For example...

I have an 8 TB volume and it contains a single 8TB LUN. Both are thin, and nightly de-dupe enabled on the volume. The ESX datastore is VMFS 6 and has space recovery enabled. Currently I have 3.4TB free on the LUN, and would expect to have more than that free on the volume, but I don't. I have 1.37TB free on the volume. There are no snapshots. 

Where do I start looking?

[Ontapforrum]

Hi,

Some pointers, do you mind taking a look at the following article, even though it has a different cDOT & ESX version but it's explaining about 'How to recover space on thinly provisioned esx lun/volume from the backend storage.

https://www.sysadmintutorials.com/tutorials/vmware-vsphere-5-x/vmware-vsphere-5-5-lun-reclaim-unmap/

In case the information in the article does not help or apply to your environment, feel free to let us know, someone will get back to you.

Thanks!

[donny_lang]

Is space allocation enabled on the LUN? This setting will allow ONTAP to reclaim space automatically when the host OS deletes data. 

lun show -vserver <vserver> -lun <lun> -fields space-allocation

Here is a document that explains the process of enabling the parameter if it is currently disabled:

https://library.netapp.com/ecmdocs/ECMP1196784/html/GUID-6AD84908-041A-497D-95A7-BB6AFDD1B282.html

[TheX]

The default setting is disabled. Is there any reason not to enable it?

[donny_lang]

I can't think of any reason not to enable it if your use case supports it (which it sounds like it does) and the workload consuming space on the LUN can accommodate the downtime needed to offline the LUN and enable the setting.