=================================
Create and manage host aggregates
=================================

Host aggregates enable administrative users to assign key-value pairs to
groups of machines.

Each node can have multiple aggregates and each aggregate can have
multiple key-value pairs. You can assign the same key-value pair to
multiple aggregates.

The scheduler uses this information to make scheduling decisions. For
information, see
`Scheduling <http://docs.openstack.org/kilo/config-reference/content/section_compute-scheduler.html>`__.

To create a host aggregate
~~~~~~~~~~~~~~~~~~~~~~~~~~

#. Log in to the dashboard.

   Choose the admin project from the drop-down list at the top of the
   page.

#. On the :guilabel:`Admin` tab, open the System Panel and click the
   :guilabel:`Host Aggregates` category.

#. Click :guilabel:`Create Host Aggregate`.

#. In the :guilabel:`Create Host Aggregate` dialog box, enter or select the
   following values on the :guilabel:`Host Aggregate Info` tab:

   -  Name: The host aggregate name.

   -  Availability Zone: The cloud provider defines the default
      availability zone, such as ``us-west``, ``apac-south``, or
      ``nova``. You can target the host aggregate, as follows:

      -  When the host aggregate is exposed as an availability zone,
         select the availability zone when you launch an instance.

      -  When the host aggregate is not exposed as an availability zone,
         select a flavor and its extra specs to target the host
         aggregate.

#. Assign hosts to the aggregate on the Host within :guilabel:`Aggregate` tab.

   To assign a host to the aggregate, click **+** for the host. The host
   moves from the :guilabel:`All available hosts` list to the
   :guilabel:`Selected hosts` list.

You can add one host to one or more aggregates. To add a host to an
existing aggregate, edit the aggregate.

To manage host aggregates
~~~~~~~~~~~~~~~~~~~~~~~~~

#. Choose the admin project from the drop-down list at the top of the
   page.

#. On the :guilabel:`Admin` tab, open the :guilabel:`System Panel` and click
   the :guilabel:`Host Aggregates` category.

   -  To edit host aggregates, select the host aggregate that you want
      to edit. Click :guilabel:`Edit Host Aggregate`.

      In the :guilabel:`Edit Host Aggregate` dialog box, you can change the
      name and availability zone for the aggregate.

   -  To manage hosts, locate the host aggregate that you want to edit
      in the table. Click :guilabel:`More` and select :guilabel:`Manage Hosts`.

      In the :guilabel:`Add/Remove Hosts to Aggregate` dialog box,
      click **+** to assign a host to an aggregate. Click **-** to
      remove a host that is assigned to an aggregate.

   -  To delete host aggregates, locate the host aggregate that you want
      to edit in the table. Click :guilabel:`More` and select
      :guilabel:`Delete Host Aggregate`.