Add documentation for Nested Quotas on Cinder
This serves as a very general introduction for nested quotas on Cinder. Change-Id: I182720b006c9ed441a476cc0d4feb2a3553f7b63
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Erickson Santos
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@ -11,6 +11,7 @@ Block Storage
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block-storage/block-storage-sample-configuration-files.rst
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block-storage/cinder-log-files.rst
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block-storage/fc-zoning.rst
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block-storage/nested-quota.rst
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block-storage/volume-encryption.rst
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block-storage/volume-misc.rst
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tables/conf-changes/cinder.rst
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170
doc/config-ref-rst/source/block-storage/nested-quota.rst
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170
doc/config-ref-rst/source/block-storage/nested-quota.rst
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=============
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Nested quotas
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=============
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Nested quota is a change in how OpenStack services (such as Block Storage and
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Compute) handle their quota resources by being hierarchy-aware. The main
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reason for this change is to fully appreciate the hierarchical multitenancy
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concept, which was introduced in keystone in the Kilo release.
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Once you have a project hierarchy created in keystone, nested quotas let you
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define how much of a project's quota you want to give to its subprojects. In
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that way, hierarchical projects can have hierarchical quotas (also known as
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nested quotas).
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Projects and subprojects have similar behaviours, but they differ from each
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other when it comes to default quota values. The default quota value for
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resources in a subproject is 0, so that when a subproject is created it will
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not consume all of its parent's quota.
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In order to keep track of how much of each quota was allocated to a
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subproject, a column ``allocated`` was added to the quotas table. This column
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is updated after every delete and update quota operation.
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This example shows you how to use nested quotas.
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.. note::
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Assume that you have created a project hierarchy in keystone, such as
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follows:
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.. code-block:: console
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+-----------+
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| |
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| A |
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| / \ |
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| B C |
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| / |
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| D |
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+-----------+
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Getting default quotas
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~~~~~~~~~~~~~~~~~~~~~~
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#. Get the quota for root projects.
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Use the cinder :command:`quota-show` command and specify:
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- The ``TENANT_ID`` of the relevant project. In this case, the id of
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project A.
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.. code-block:: console
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$ cinder quota-show TENANT_ID
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+-----------------------+-------+
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| Property | Value |
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+-----------------------+-------+
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| backup_gigabytes | 1000 |
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| backups | 10 |
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| gigabytes | 1000 |
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| gigabytes_lvmdriver-1 | -1 |
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| per_volume_gigabytes | -1 |
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| snapshots | 10 |
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| snapshots_lvmdriver-1 | -1 |
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| volumes | 10 |
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| volumes_lvmdriver-1 | -1 |
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+-----------------------+-------+
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.. note::
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This command returns the default values for resources.
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This is because the quotas for this project were not explictly set.
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#. Get the quota for subprojects.
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In this case, use the same :command:`quota-show` command and specify:
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- The ``TENANT_ID`` of the relevant project. In this case the id of
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project B, which is a child of A.
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.. code-block:: console
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$ cinder quota-show TENANT_ID
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+-----------------------+-------+
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| Property | Value |
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+-----------------------+-------+
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| backup_gigabytes | 0 |
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| backups | 0 |
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| gigabytes | 0 |
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| gigabytes_lvmdriver-1 | 0 |
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| per_volume_gigabytes | 0 |
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| snapshots | 0 |
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| snapshots_lvmdriver-1 | 0 |
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| volumes | 0 |
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| volumes_lvmdriver-1 | 0 |
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+-----------------------+-------+
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.. note::
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In this case, 0 was the value returned as the quota for all the
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resources. This is because project B is a subproject of A, thus,
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the default quota value is 0, so that it will not consume all the
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quota of its parent project.
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Setting the quotas for subprojects
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Now that the projects were created, assume that the admin of project B wants
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to use it. First of all, you need to set the quota limit of the project,
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because as a subproject it does not have quotas allocated by default.
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In this example, when all of the parent project is allocated to its
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subprojects the user will not be able to create more resources in the parent
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project.
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#. Update the quota of B.
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Use the :command:`quota-update` command and specify:
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- The ``TENANT_ID`` of the relevant project.
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In this case the id of project B.
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- The ``--volumes`` option, followed by the number to which you wish to
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increase the volumes quota.
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.. code-block:: console
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$ cinder quota-update TENANT_ID --volumes 10
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+-----------------------+-------+
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| Property | Value |
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+-----------------------+-------+
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| backup_gigabytes | 0 |
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| backups | 0 |
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| gigabytes | 0 |
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| gigabytes_lvmdriver-1 | 0 |
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| per_volume_gigabytes | 0 |
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| snapshots | 0 |
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| snapshots_lvmdriver-1 | 0 |
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| volumes | 10 |
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| volumes_lvmdriver-1 | 0 |
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+-----------------------+-------+
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.. note::
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The volumes resource quota is updated.
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#. Try to create a volume in project A.
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Use the :command:`create` command and specify:
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- The ``SIZE`` of the volume that will be created;
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- The ``NAME`` of the volume.
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.. code-block:: console
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$ cinder create --size SIZE NAME
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VolumeLimitExceeded: Maximum number of volumes allowed (10) exceeded for quota 'volumes'. (HTTP 413) (Request-ID: req-f6f7cc89-998e-4a82-803d-c73c8ee2016c)
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.. note::
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As the entirety of project A's volumes quota has been assigned to
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project B, it is treated as if all of the quota has been used. This
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is true even when project B has not created any volumes.
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See `cinder nested quota spec
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<http://specs.openstack.org/openstack/cinder-specs/specs/liberty/cinder-nested-quota-driver.html>`_
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and `hierarchical multitenancy spec
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<https://blueprints.launchpad.net/keystone/+spec/hierarchical-multitenancy>`_
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for details.
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