Hello, I googled for my issue and I found the following:
https://bugs.launchpad.net/neutron/+bug/1866139
Regards Ignazio
Il giorno lun 27 apr 2020 alle ore 19:50 Sean Mooney smooney@redhat.com ha scritto:
On Mon, 2020-04-27 at 18:19 +0200, Ignazio Cassano wrote:
Hello, I have this problem with rocky or newer with iptables_hybrid firewall. So, can I solve using post copy live migration ???
so this behavior has always been how nova worked but rocky the
https://specs.openstack.org/openstack/nova-specs/specs/rocky/implemented/neu... spec intoduced teh ablity to shorten the outage by pre biding the port and activating it when the vm is resumed on the destiation host before we get to pos live migrate.
this reduces the outage time although i cant be fully elimiated as some level of packet loss is always expected when you live migrate.
so yes enabliy post copy live migration should help but be aware that if a network partion happens during a post copy live migration the vm will crash and need to be restarted. it is generally safe to use and will imporve the migration performace but unlike pre copy migration if the guess resumes on the dest and the mempry page has not been copied yet then it must wait for it to be copied and retrive it form the souce host. if the connection too the souce host is intrupted then the vm cant do that and the migration will fail and the instance will crash. if you are using precopy migration if there is a network partaion during the migration the migration will fail but the instance will continue to run on the source host.
so while i would still recommend using it, i it just good to be aware of that behavior change.
Thanks Ignazio
Il Lun 27 Apr 2020, 17:57 Sean Mooney smooney@redhat.com ha scritto:
On Mon, 2020-04-27 at 17:06 +0200, Ignazio Cassano wrote:
Hello, I have a problem on stein neutron. When a vm migrate from one
node
to another I cannot ping it for several minutes. If in the vm I put a script that ping the gateway continously, the live migration works
fine
and
I can ping it. Why this happens ? I read something about gratuitous
arp.
qemu does not use gratuitous arp but instead uses an older protocal
called
RARP to do mac address learning.
what release of openstack are you using. and are you using iptables firewall of openvswitch firewall.
if you are using openvswtich there is is nothing we can do until we finally delegate vif pluging to os-vif. currently libvirt handels interface plugging for kernel ovs when using
the
openvswitch firewall driver https://review.opendev.org/#/c/602432/ would adress that but it and
the
neutron patch are https://review.opendev.org/#/c/640258 rather out dated. while libvirt
is
pluging the vif there will always be a race condition where the RARP packets sent by qemu and then mac
learning
packets will be lost.
if you are using the iptables firewall and you have opnestack rock or later then if you enable post copy live migration it should reduce the downtime. in this conficution we do not have the
race
betwen neutron and libvirt so the rarp packets should not be lost.
Please, help me ? Any workaround , please ?
Best Regards Ignazio