If using "vmware.hv.datastore.size" item keys directly on a ESXi host, the item becomes not supported.

However, when the same key is used on a vCenter server (i.e. not directly on a ESXi host, but via a vCenter host), the item works fine and returns valid values.

This prevents monitoring VMware ESXi nodes datastores if they are not connected to vCenter (standalone), and ugly workaround scripts need to be used instead (querying VMware API).