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===============================
Basic volume quality of service
===============================
Basic volume QoS allows you to define hard performance limits for volumes
on a per-volume basis.
Performance parameters for attached volumes are controlled using volume types
and associated extra-specs.
As of the 13.0.0 Rocky release, Cinder supports the following options to
control volume quality of service, the values of which should be fairly
self-explanatory:
For Fixed IOPS per volume.
* `read_iops_sec`
* `write_iops_sec`
* `total_iops_sec`
For Burst IOPS per volume.
* `read_iops_sec_max`
* `write_iops_sec_max`
* `total_iops_sec_max`
For Fixed bandwidth per volume.
* `read_bytes_sec`
* `write_bytes_sec`
* `total_bytes_sec`
For Burst bandwidth per volume.
* `read_bytes_sec_max`
* `write_bytes_sec_max`
* `total_bytes_sec_max`
For burst bucket size.
* `size_iops_sec`
Note that the `total_*` and `total_*_max` options for both iops and bytes
cannot be used with the equivalent `read` and `write` values.
For example, in order to create a QoS extra-spec with 20000 read IOPs and
10000 write IOPs, you might use the Cinder client in the following way:
.. code-block:: console
$ cinder qos-create high-iops consumer="front-end" \
read_iops_sec=20000 write_iops_sec=10000
+----------+--------------------------------------+
| Property | Value |
+----------+--------------------------------------+
| consumer | front-end |
| id | f448f61c-4238-4eef-a93a-2024253b8f75 |
| name | high-iops |
| specs | read_iops_sec : 20000 |
| | write_iops_sec : 10000 |
+----------+--------------------------------------+
The equivalent OpenStack client command would be:
.. code-block:: console
$ openstack volume qos create --consumer "front-end" \
--property "read_iops_sec=20000" \
--property "write_iops_sec=10000" \
high-iops
Once this is done, you can associate this QoS with a volume type by using
the `qos-associate` Cinder client command.
.. code-block:: console
$ cinder qos-associate QOS_ID VOLUME_TYPE_ID
or using the `openstack volume qos associate` OpenStack client command.
.. code-block:: console
$ openstack volume qos associate QOS_ID VOLUME_TYPE_ID
You can now create a new volume and attempt to attach it to a consumer such
as Nova. If you login to the Nova compute host, you'll be able to see the
assigned limits when checking the XML definition of the virtual machine
with `virsh dumpxml`.
.. note::
As of the Nova 18.0.0 Rocky release, front end QoS settings are only
supported when using the libvirt driver.
|
