Windows Server 2016, ONTAP 9.5, LUN is thin, NTFS formatted, space-allocation WAS NOT enabled
On the host side LUN is 70% occupied, on the storage side, it is 100% full. On Windows, DisableDeleteNotify = 0
After reading several KBs, I am still in doubt. Some say you cannot enable space-allocation with the LUN online, some say you need to reboot the server after enabling it, some say you can enable space-allocation and just run a rescan on the host side.
Fact is that after enabling it with the LUN online and running a rescan, blocks are still provisioned on the storage side. I tried to create a new file inside the LUN and then delete it (there's a KB stating that this could trigger the UNMAP process). No luck.
Just going by the official NetApp documentation (Not kbs), it does clearly state: You must take the LUN offline to enable space allocation. I think if you just follow the 5 steps in the doc below, it should work.
I read that line - Modern OS, it is confusing, and I wonder which OS , further even if the Host is re-sending the scsi_inquiry (as part of the scsi_bus_scan) it is still picking up "old" data from the storage. Therefore, LUN must be taken offline so that the "SCSI inquiry" data on both nodes in the HA pair is updated.