1d222ac16f
In I808227fe71210abc64270f53ef3d3d62f176ff24 we approved to remove the Priorities section. Now it's a cleanup for the already accepted specs. Change-Id: I6bf243ca114a72cd71aa97491eb528312c53a0dd
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This work is licensed under a Creative Commons Attribution 3.0 Unported
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License.
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http://creativecommons.org/licenses/by/3.0/legalcode
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==========================================
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Hyper-V Storage QoS
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==========================================
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https://blueprints.launchpad.net/nova/+spec/hyperv-storage-qos
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Hyper-V provides options to specify maximum IOPS per virtual disk image.
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By leveraging this feature, this blueprint proposes to add support for setting
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QoS specs targeting instance local disks as well as volumes exported through
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SMB.
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Problem description
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===================
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At the moment, the Nova Hyper-V driver does not support setting storage IOPS
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limits. For this reason, some instances might exhaust storage resources,
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impacting other tenants.
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Use Cases
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----------
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* Associate front-end QoS specs for volumes exported through SMB, which will
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be handled on the hypervisor side
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* Set IOPS caps for instance local disks by using flavor extra specs
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Proposed change
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===============
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Cinder volumes can have QoS specs assigned. Front-end QoS specs should be
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applied by Nova when the volume is attached. Those are applied per volume.
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In addition, this blueprint proposes per instance QoS specs that will be
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specified using flavor extra specs. The Hyper-V driver will apply those IOPS
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caps to all the local instance disks equally.
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For example, if a specific IOPS cap is specified in the flavor extra specs,
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this cap will be applied to the instance root, ephemeral and configdrive disk
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equally.
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Front-end volume specs will be supported only in case of volumes exported
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through SMB.
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Use case examples:
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* Admin sets front-end QoS specs on a specific volume type
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cinder qos-create my-qos consumer=front-end \
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total_bytes_sec=20971520 \
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cinder qos-associate my-qos <volume_type_id>
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# SMB must be used as a volume backend, iSCSI support may be
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# added in the future
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cinder create <size> --volume-type <volume_type_id>
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# Those QoS specs are applied when the volume is
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# attached to a Hyper-V instance
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nova volume-attach <hyperv_instance_id> <volume_id>
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* Admin sets instance storage QoS specs on the flavor
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nova flavor-key <my_flavor> set \
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storage_local_qos:total_bytes_sec=20971520
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Available QoS specs:
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* total_bytes_sec - includes read/writes
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* total_iops_sec
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Alternatives
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------------
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Flavor QoS specs could be applied not only for instance local disks but
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attached volumes as well. In this case, if volume QoS specs are present, we may
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apply the lowest IOPS cap.
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Also, the cap could be divided among the disks, but this may not be desired.
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Data model impact
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-----------------
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None
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REST API impact
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---------------
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None
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Security impact
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---------------
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Setting storage QoS specs will prevent instances from exhausting storage
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resources, which may impact other tenants.
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Notifications impact
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--------------------
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None
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Other end user impact
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---------------------
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None
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Performance Impact
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------------------
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Preventing instances from exhausting storage resources can have a significant
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performance impact.
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Other deployer impact
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---------------------
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None
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Developer impact
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----------------
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None
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Implementation
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==============
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Assignee(s)
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-----------
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Primary assignee:
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Lucian Petrut <lpetrut@cloudbasesolutions.com>
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Work Items
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----------
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* Add front-end QoS specs support in the Hyper-V SMB volume driver
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* Add flavor storage QoS specs support
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Dependencies
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============
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None
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Testing
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=======
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This feature will be tested by the Hyper-V CI. We'll add tempest tests
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verifying that the IOPS cap is actually enforced.
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Documentation Impact
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====================
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The QoS features should be described in the Hyper-V driver documentation.
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References
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==========
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Hyper-V Storage QoS reference:
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https://technet.microsoft.com/en-us/library/dn282281.aspx
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History
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=======
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None
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