Cannot umount lun from host in ESXi

I am using ESXi 6.0 cluster with few hosts.
I need to umount/detach datastores related to an old storage that should be removed from datacenter.
Basically I am following this:

While umounting specific lun from one specific host, I encountered a waring message (like this lun is used somewhere).

I noticed a VM which seems to have references to such datastore:

storage1 lun 9 and storage2 lun 1 are definitely empty.

I suspect this could be related to some previous snapshot, but I am not sure.

How can I "force" the umount in that case?

Thank you!
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
You need to make sure it's not in use, if it's not in use, it cannot be unmounted.....

Have you checked Datastore Inventory, to check if any host is still using it, e.g. isos, floppy disks, VMs etc

or object is attached to it. If you have found a VM, Edit the Settings and check if there is any reference to it.... e.g. disk, cdrom iso, floppy disk etc
Armitage318Author Commented:
I do confirm that such lun is empty. No iso, no floppy, no virtual disk.
If I click on Edit Settings, I don't see any reference to ISO image

the virtual disk is on storage4 lun6, so it is not on datastore that I need to remove (storage1).
Thank you
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
what does Datastore Inventory show any objects attached to the datastore

If you select Unmount, it usually shows a number of green ticks, and then stops.....

what item does it stop on ?
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Luciano PatrãoICT Senior Infraestructure  Engineer  Commented:

Do you have any snapshots from those VMs that were inside the Datastore you want to unmount? Because any snapshots that was created on a VM when was running on that Datastore will prevent the Datastore to be unmounted.

Solution is to delete Snapshots.

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Hani M .S. Al-habshiContributor as IT ExpertCommented:
Do you have data store Snapshots ? if yes remove them
Armitage318Author Commented:
Hi Andrew, the first one: "No virtual machine resides on datastore".

Hi Luciano, yes, as I wrote on first post, I do have snapshot. Does issue occours even if snapshot NOT resides on that lun (again, which is totally empty)?
Than you
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
If there is a reference to the LUN - yes.

What does Datastore Inventory state for that Datastore/LUN ?
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