Serial execution need to be documented. Here is few words about the feature: To run parallel Ansible update on the nodes, TripleO is using the value of the update_serial variable located in the roles_data.yaml. This value is present on the latest roles_data.yaml that comes with tripleo-heat-templates. The default value doesn't allow to run parallel execution on Controller nodes, which is not supported and recomanded by the Eng. The default value for the Compute is 25. To update the update_serial value with your own value you need to: 1/ run prepare step with the updated roles_data.yaml (if you use the default in THT, you can just edit the update_serial value) https://github.com/openstack/tripleo-heat-templates/blob/master/roles_data.yaml#L37 If you use a custom roles_data file, you need to update the file to add the update_serial value. 2/ run the step 2: openstack overcloud update run --nodes Computes All the compute should be updated at the same time, or according to the value of update_serial.
Adding update_serial for OSP13 and OSP14: https://access.redhat.com/documentation/en-us/red_hat_openstack_platform/13/html/advanced_overcloud_customization/roles#Examining_Composable_Role_Parameters https://access.redhat.com/documentation/en-us/red_hat_openstack_platform/14/html/advanced_overcloud_customization/roles#Examining_Composable_Role_Parameters Have also updated for OSP15. Closing BZ.