For this purpose I indicate this official Veeam tutorial to get this result.
http://files.qnap.com/news/pressresource/product/How_to_set_up_QNAP_NAS_as_a_datastore_via_iSCSI_for_VMware_ESX_4.0_or_above.pdf
The main idea is to expose storage with ISCSI and then connect it to Vmware ESXi.
The best approach it would be to have double switch (for redundancy) and different paths availibility (in this mode) and create a VLAN between ESX(i) and QNAP storage (but it work in any case on same VLAN where there are clients/servers too but with less perfomances)
InfraStructure
QNAP screenshot lun creation
ESXI lun connection
Now Status is enabled
Here they are updated links to all QNAP Storage products:
https://www.qnap.com/it-it/product/
