Reproposes Hyper-V Storage QOS spec to Newton

Previously-approved: Liberty, Mitaka

Change-Id: Id85ed00a20b88286c9f6273c4039695103feac18
Implements: blueprint hyperv-storage-qos

specs/newton/approved/hyperv-storage-qos.rst

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