hw_scsi_model from glance image is not used when booting instance from new volume

[Logan V]

When creating an instance backed by a cinder volume, the disk device /dev/vda is used regardless of image settings. I am using the following image metadata to set virtio-scsi driver on my instances:
hw_disk_bus=scsi
hw_scsi_model=virtio-scsi

When I boot instances using a normal root device ("boot from image"), they are using /dev/sda and virtio-scsi as expected. When booting from volume (either with a new volume or an existing image-based volume), they use "<target dev='vda' bus='virtio'/>", ignoring the image metadata.

According to this spec: http://specs.openstack.org/openstack/nova-specs/specs/juno/approved/add-virtio-scsi-bus-for-bdm.html

A "work item" was: "Nova retrieve “hw_scsi_model” property from volume’s glance_image_metadata when booting from cinder volume"

I would expect this work is what would implement setting virtio-scsi on volume backed instances, however none of the reviews I have looked through for that spec appear to implement anything regarding volume backed instances.

[Logan V (loganv)]

I was able to work around this.. can_set_mount_point is false by default so I didn't realize that horizon is sending the 'vda' device name. After changing this to sda, the instance is now created with bus=scsi.

Modification made was:
    device_name = forms.CharField(label=_("Device Name"),
                                  required=False,
                                  initial="sda",
                                  help_text=_("Volume mount point (e.g. 'vda' "
                                              "mounts at '/dev/vda'). Leave "
                                              "this field blank to let the "
                                              "system choose a device name "
                                              "for you."))

changed initial="vda" to initial="sda"

This field was hidden by default and the instance has metadata saying to use the scsi bus, so I am still thinking this is some sort of bug. Maybe the dashboard should not send a device name if the field is not visible?

[jichenjc (jichenjc)]

seems not related to nova based on #1

[Gary W. Smith (gary-w-smith)]

This appears to be a duplicate of 1560965; although this bug was entered first, the other has more information and progress.