Add virtio-scsi bus support for block device mapping

Add virtio-scsi bus support for block device mapping

https://blueprints.launchpad.net/nova/+spec/add-virtio-scsi-bus-for-bdm

VirtIO SCSI is a new para-virtualized SCSI controller device for KVM instances. It has been designed to replace virtio-blk, increase it’s performance and improve scalability. Currently, using virtio-scsi bus is not supported when booting from volume.

Problem description

VirtIO SCSI is a new para-virtualized SCSI controller device for KVM instances. It has been designed to replace virtio-blk, increase it’s performance and improve scalability. The interface is capable of handling multiple block devices per virtual SCSI adapter, keeps the standard scsi device naming in the guests (e.x /dev/sda) and support SCSI devices passthrough.

Currently, virtio-scsi bus has been supported when booting from glance image, which is implemented by BP ([1]) aimed to Icehouse.

However, when we create a cinder volume from this image, and then booting from this volume and specify the bus_type as “scsi”, the guest will still use lsi controller instead of virtio-scsi controller.

The aim of this BP as follows:

When booting from volume with “scsi” bus type, use virtio-scsi controller for volume which was created from glance image, which is set with “virtio-scsi” hw_scsi_model property.

The main use case is to improve performance in I/O-intensive applications.

Proposed change

  • Nova retrieve “hw_scsi_model” property from volume’s glance_image_metadata when booting from cinder volume

  • Libvirt driver will create the “virtio-scsi” controller if “hw_scsi_model” property is “virtio-scsi” and the bus_type specified for volume is “scsi”

Alternatives

None

Data model impact

None

REST API impact

None

Security impact

None

Notifications impact

None

Other end user impact

None

Performance Impact

Will improve guest’s performance.

Other deployer impact

None

Developer impact

None

Implementation

Assignee(s)

Primary assignee:

<zhangleiqiang@huawei.com>

Work Items

  • Nova retrieve “hw_scsi_model” property from volume’s glance_image_metadata when booting from cinder volume

  • Libvirt driver will create the “virtio-scsi” controller if “hw_scsi_model” property is “virtio-scsi” and the bus_type specified for volume is “scsi”

Dependencies

  • Depend on the BP [1], which will provide the virtio-scsi-controller object

Testing

None

Documentation Impact

None

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nova-specs