[ovs-discuss] [ovn] recommendation to gateway chassis

Numan Siddique numans at ovn.org
Fri Apr 16 11:15:42 UTC 2021


On Thu, Apr 15, 2021 at 11:27 PM Tony Liu <tonyliu0592 at hotmail.com> wrote:
>
> Any comments?
>
> Thanks!
> Tony
> > -----Original Message-----
> > From: discuss <ovs-discuss-bounces at openvswitch.org> On Behalf Of Tony
> > Liu
> > Sent: Saturday, April 3, 2021 12:05 PM
> > To: ovs-discuss <ovs-discuss at openvswitch.org>
> > Subject: [ovs-discuss] [ovn] recommendation to gateway chassis
> >
> > Hi,
> >
> > For now, I have a setup with DVR to route FIP traffic directly on
> > compute node and dedicated central GWs to handle SNAT traffic.
> > Then I realize that I can put GW chassis on compute node as well.
> > Is this recommended over dedicated GW chassis?

>From what I know, OpenStack neutron uses this approach of using
networker/controller
nodes for SNAT traffic.

I think from an OVN perspective, it doesn't matter if you chose to use
a compute node for
SNAT traffic or use controller/networker nodes, because even a
controller/networker node
is registered as a chassis and ovn-controller runs there.

The only difference would be controller/networker nodes most likely
will not have any VMs/pods scheduled.


> >
> > If yes, is there any difference between 1) picking up a few compute
> > nodes as GW and 2) putting GW on all compute nodes (like 200 nodes), in
> > terms of the impact to OVN control plane and data plane, like DB sizing
> > and handling, performance, health check peering, etc.?

If you chose (2), I think there may be more BFD sessions compared to (1).

Let's say you chose compute nodes 1, 2 and 3 as your GW nodes and they
are part of
a gateway chassis list, then there will be BFD session established
between (1,2), (1, 3) and (2,3)
Additionally there will be BFD sessions from a compute node X to 1, 2
and 3 if node X has a VIF
bound which connects to the distributed gateway logical router.

I think you need to keep these things in mind before choosing to
select all compute nodes or just a select few
as your GW nodes.

I don't think there should be any impact on the control plane whether
you choose (1) or (2).

Thanks
Numan


> >
> > Or the question is that, what's the comfortable scale of gateway chassis
> > in OVN. If it's a few hundreds, then having GW on all compute nodes
> > would be the best option.
> >
> > Any comment is appreciated.
> >
> >
> > Thanks!
> > Tony
> >
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