1. Goto datastore views in the vsphere client/webclient and check virtual machine tab to see if there are any virtual machine running from this DS.
2. Check if this datastore is configured as a HA heartbeat datastore for any cluster , that will block removing the datastore.
can you please post this output from ssh session of esxi host
1. go to datastore location
3. touch *
4. ls -al
Also perform a rescan once and try deleting the DS again.
can you run this command and post the output
vmkfstools -D /vmfs/volumes/<ds name>/vmkdump
looks like this DS has been configured as a dump partition for one of the hosts
try to delete the datastore again and share the vmkernel log file from the host for that timestamp.. if you can share logs
I got burned by this and it turned out that I had a template on the datastore I wanted to delete. I had to convert the template into a vm an then move it off the datastore. I was thinking it was a dump lock file or something else more complex.
Hope this is the case for you to.