[openstack-dev] [nova]Why not allow to create a vm directly with two VIF in the same network

Daniel P. Berrange berrange at redhat.com
Fri Jan 24 15:00:13 UTC 2014

On Fri, Jan 24, 2014 at 02:11:02PM +0000, Day, Phil wrote:
> I agree its oddly inconsistent (you'll get used to that over time ;-)
>  - but to me it feels more like the validation is missing on the attach
> that that the create should allow two VIFs on the same network.   Since
> these are both virtualised (i.e share the same bandwidth, don't provide
> any additional resilience, etc) I'm curious about why you'd want two VIFs
> in this configuration ?

Whether it has benefits or not will depend on the type of network
configuration being used. If the guest virtual NICs are connected to
a physical NIC that is an SRIOV device using macvtap, then there is
certainly potential for performance benefits. ie each of the VIFs
could be connected to a separate virtual function on the physical
NIC, and so benefit from separate transmit queues in the hardware.

NB, this is somewhat academic wrt openstack though, since I don't
believe any of the NIC configs we support can do this kind of
cleverness macvtap configs.

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