[ovs-discuss] Transferring OVS port data on migration

[Michal Privoznik]

Hi,

I'm a libvirt developer and recently we were asked the following on our 
list:

   https://www.redhat.com/archives/libvir-list/2019-May/msg00851.html


Long story short, when libvirt is migrating a virtual machine that has a 
NIC plugged into OVS then in the last phase when VM is suspended on the 
source libvirt fetches internal state of OVS (port data), transfers it 
to the destination and restores it there:

   ovs-vsctl --if-exists get Interface $ifname external_ids:PortData

   ovs-vsctl set Interface $ifname external_ids:PortData=$data

According to the linked e-mail in some cases there is no data to 
transfer and thus this adds unnecessary downtime for VMs.

My question is, is what libvirt is doing still necessary (the code was 
added to libvirt 7 years ago)? Is there a better way to transfer 
internal state of OVS?

Thanks,
Michal