Comment 8 for bug 1849802

by the way --live is deprecated since it does a force migration and is remvoed in later microversoins you should use --live-migration and --host if you want to select a host.

  --live-migration Live migrate the server. Use the ``--host`` option to specify a target host for the migration which will be validated by the scheduler.
  --live <hostname> **Deprecated** This option is problematic in that it requires a host and prior to compute API version 2.30, specifying a host during live migration will bypass validation by the scheduler
                        which could result in failures to actually migrate the server to the specified host or over-subscribe the host. Use the ``--live-migration`` option instead. If both this option and
                        ``--live-migration`` are used, ``--live-migration`` takes priority.
  --host <hostname> Migrate the server to the specified host. Requires ``--os-compute-api-version`` 2.30 or greater when used with the ``--live-migration`` option, otherwise requires ``--os-compute-api-
                        version`` 2.56 or greater.

if you use --live-migration and --host the schduler will check the instance can actuly fit and is appropriate for the host. if you use --live you as the admin have to manually validate that because you are forceing the migration which can lead to broken states.

our expreince over the year is that allowing the operator to force evacuations or live migration has done more harm then good over the years so we remvoed that in microverion 2.68
https://docs.openstack.org/nova/latest/reference/api-microversion-history.html#id62

you can still do it with the old microverion but if you can avoid it you should.