f0b8204072
As discussed at our nova meetings, reorganize the juno specs into three directories: - proposed: things proposed which weren't approved - approved: things we approved but didn't implement - implemented: things approved and implemented The first I suspect is the most controversial. I've done this because I worry about the case where a future developer wants to pick up something dropped by a previous developer, but has trouble finding previous proposed specifications on the topic. Note that the actual proposed specs for Juno are adding in a later commit. Change-Id: Idcf55ca37a83d7098dcb7c2971240c4e8fd23dc8
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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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Add virtio-scsi bus support for block device mapping
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=====================================================
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https://blueprints.launchpad.net/nova/+spec/add-virtio-scsi-bus-for-bdm
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VirtIO SCSI is a new para-virtualized SCSI controller device for KVM instances.
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It has been designed to replace virtio-blk, increase it's performance and
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improve scalability. Currently, using virtio-scsi bus is not supported when
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booting from volume.
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Problem description
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===================
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VirtIO SCSI is a new para-virtualized SCSI controller device for KVM instances.
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It has been designed to replace virtio-blk, increase it's performance and
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improve scalability. The interface is capable of handling multiple block
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devices per virtual SCSI adapter, keeps the standard scsi device naming
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in the guests (e.x /dev/sda) and support SCSI devices passthrough.
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Currently, virtio-scsi bus has been supported when booting from glance image,
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which is implemented by BP ([1]) aimed to Icehouse.
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However, when we create a cinder volume from this image, and then booting
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from this volume and specify the bus_type as "scsi", the guest will still
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use lsi controller instead of virtio-scsi controller.
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The aim of this BP as follows:
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When booting from volume with "scsi" bus type, use virtio-scsi controller
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for volume which was created from glance image, which is set with
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"virtio-scsi" hw_scsi_model property.
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The main use case is to improve performance in I/O-intensive applications.
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Proposed change
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===============
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* Nova retrieve "hw_scsi_model" property from volume's glance_image_metadata
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when booting from cinder volume
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* Libvirt driver will create the "virtio-scsi" controller if "hw_scsi_model"
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property is "virtio-scsi" and the bus_type specified for volume is "scsi"
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Alternatives
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------------
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None
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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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None
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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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Will improve guest's performance.
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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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<zhangleiqiang@huawei.com>
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Work Items
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----------
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* Nova retrieve "hw_scsi_model" property from volume's glance_image_metadata
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when booting from cinder volume
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* Libvirt driver will create the "virtio-scsi" controller if "hw_scsi_model"
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property is "virtio-scsi" and the bus_type specified for volume is "scsi"
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Dependencies
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============
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* Depend on the BP [1], which will provide the virtio-scsi-controller object
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Testing
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=======
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None
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Documentation Impact
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====================
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None
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References
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==========
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* [1] https://blueprints.launchpad.net/nova/+spec/libvirt-virtio-scsi-driver
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