# Set CPU Allocation Ratio For Host Aggregate

## Problem

It is desired to over-provision CPU cores on a subset of hosts instead of provisioning it for the OpenStack environment as a whole. A CPU allocation ratio parameter may be set as metadata for a particular host aggregate containing that subset of hosts.

## Environment

* Platform9 Managed OpenStack - v3.11 and Lower
* Nova

## Prerequisites

* ***AggregateCoreFilter*** must be set in */etc/nova/nova.conf* on the Management Plane.

**Note**: If you're uncertain if this is set, [submit a ticket](https://support.platform9.com/hc/en-us/requests/new?ticket_form_id=360000924873) to Platform9 Support to check and have it enabled.

## Procedure

1. Navigate to the "Infrastructure" tab in Clarity UI.
2. Select the "Host Aggregates" tab.
3. Select the host aggregate you intend to modify (assuming one has already been created).
4. Click "Edit Host Aggregate".
5. In the Metadata section, select "Add key-value metadata".
6. Specify the ***Key*** as ***cpu\_allocation\_ratio*** and the ***Value*** as the intended ratio, e.g. ***2.0***.

<figure><img src="/files/DbkprCksvWZxHPKoLXjQ" alt="Screen_Shot_2019-10-31_at_5.06.42_PM.png"><figcaption><p>Screen_Shot_2019-10-31_at_5.06.42_PM.png</p></figcaption></figure>

7. Click "Save".

## Additional Information

[OpenStack Docs: Overcommitting CPU and RAM](https://docs.openstack.org/arch-design/design-compute/design-compute-overcommit.html)


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