A LUN Is displaying 90% used space in the NetApp ONTAP CLI, but a Windows...

When a LUN shows 90% used space in the NetApp ONTAP CLI but a Windows Server shows only 10% used space, the discrepancy is often due to how space allocation is handled between the two systems. Enabling space allocation ensures that the ONTAP system accurately reflects the actual space usage as reported by the host system, in this case, the Windows Server. This adjustment allows ONTAP to reclaim and manage space more effectively, aligning the reported usage between the ONTAP system and the host.

For more information, refer to:

NetApp Community Discussion on Space Allocation

NetApp Documentation on Space Usage