Comment 2 for bug 1930406

I can't capture it in an update here but uwsgitop graphically demonstrates this as well.

I've wanted to drop the RPC call to reserve_block_device_name on the compute for a while as the virt drivers can't guarantee the assigned device name within the guestOS and it's just quicker to create our BDMs in the API workers before returning:

https://docs.openstack.org/nova/latest/reference/attach-volume.html

This would require a microversion as the response of os-volume_attachments would change, making device optional:

https://docs.openstack.org/api-ref/compute/?expanded=attach-a-volume-to-an-instance-detail#attach-a-volume-to-an-instance

I can try to write up a spec for this in the coming days.