======
Ironic
======

Introduction
------------

The ironic hypervisor driver wraps the Bare Metal (ironic) API,
enabling Nova to provision baremetal resources using the same
user-facing API as for server management.

This is the only driver in nova where one compute service can map to many
hosts, meaning a ``nova-compute`` service can manage multiple ``ComputeNodes``.
An ironic driver managed compute service uses the ironic ``node uuid`` for the
compute node ``hypervisor_hostname`` (nodename) and ``uuid`` fields.  The
relationship of ``instance:compute node:ironic node`` is 1:1:1.

Scheduling of bare metal nodes is based on custom resource classes, specified
via the ``resource_class`` property on a node and a corresponding resource
property on a flavor (see the :ironic-doc:`flavor documentation
</install/configure-nova-flavors.html>`).
The RAM and CPU settings on a flavor are ignored, and the disk is only used to
determine the root partition size when a partition image is used (see the
:ironic-doc:`image documentation
</latest/install/configure-glance-images.html>`).


Configuration
-------------

- :ironic-doc:`Configure the Compute service to use the Bare Metal service
  </latest/install/configure-compute.html>`.

- :ironic-doc:`Create flavors for use with the Bare Metal service
  </latest/install/configure-nova-flavors.html>`.

- :ironic-doc:`Conductors Groups </admin/conductor-groups.html>`.


Scaling and performance issues
------------------------------

- The ``update_available_resource`` periodic task reports all the resources
  managed by Ironic. Depending the number of nodes, it can take a lot of time.
  The nova-compute will not perform any other operations when this task is
  running. You can use conductor groups to help scale, by setting
  :oslo.config:option:`ironic.partition_key`.


Known limitations / Missing features
------------------------------------

* Migrate
* Resize
* Snapshot
* Pause
* Shelve
* Evacuate