Looks like the libvirt driver is the only driver that implements the block_stats() method, and it that method encounters an error it logs it and returns None:
https://github.com/openstack/nova/blob/6bf11e1dc14afad78b11d980c2544a3dc41579ff/nova/virt/libvirt/driver.py#L6364
Looks like the libvirt driver is the only driver that implements the block_stats() method, and it that method encounters an error it logs it and returns None:
https:/ /github. com/openstack/ nova/blob/ 6bf11e1dc14afad 78b11d980c2544a 3dc41579ff/ nova/virt/ libvirt/ driver. py#L6364