[ClusterLabs] Antw: Re: Antw: [EXT] Node fenced for unknown reason

Klaus Wenninger kwenning at redhat.com
Fri Apr 16 03:17:03 EDT 2021

On 4/16/21 8:09 AM, Steffen Vinther Sørensen wrote:
> On Fri, Apr 16, 2021 at 6:56 AM Andrei Borzenkov <arvidjaar at gmail.com> wrote:
>> On 15.04.2021 23:09, Steffen Vinther Sørensen wrote:
>>> On Thu, Apr 15, 2021 at 3:39 PM Klaus Wenninger <kwenning at redhat.com> wrote:
>>>> On 4/15/21 3:26 PM, Ulrich Windl wrote:
>>>>>>>> Steffen Vinther Sørensen <svinther at gmail.com> schrieb am 15.04.2021 um
>>>>> 14:56 in
>>>>> Nachricht
>>>>> <CALhdMBiXZoYF-Gxg82oNT4MGFm6Q-_imCeUVHyPgWKy41JjFSg at mail.gmail.com>:
>>>>>> On Thu, Apr 15, 2021 at 2:29 PM Ulrich Windl
>>>>>> <Ulrich.Windl at rz.uni-regensburg.de> wrote:
>>>>>>>>>> Steffen Vinther Sørensen <svinther at gmail.com> schrieb am 15.04.2021 um
>>>>>>> 13:10 in
>>>>>>> Nachricht
>>>>>>> <CALhdMBhMQRwmgoWEWuiGMDr7HfVOTTKvW8=NQMs2P2e9p8y9Jw at mail.gmail.com>:
>>>>>>>> Hi there,
>>>>>>>> In this 3 node cluster, node03 been offline for a while, and being
>>>>>>>> brought up to service. Then a migration of a VirtualDomain is being
>>>>>>>> attempted, and node02 is then fenced.
>>>>>>>> Provided is logs from all 2 nodes, and the 'pcs config' as well as a
>>>>>>>> bzcatted pe-warn. Anyone with an idea of why the node was fenced ? Is
>>>>>>>> it because of the failed ipmi monitor warning ?
>>>>>>> After a short glace it looks as if the network traffic used for VM
>>>>> migration
>>>>>>> killed the corosync (or other) communication.
>>>>>> May I ask what part is making you think so ?
>>>>> The part that I saw no reason for an intended fencing.
>>>> And it looks like node02 is being cut off from all
>>>> networking-communication - both corosync & ipmi.
>>>> May really be the networking-load although I would
>>>> rather bet on something more systematic like a
>>>> Mac/IP-conflict with the VM or something.
>>>> I see you are having libvirtd under cluster-control.
>>>> Maybe bringing up the network-topology destroys the
>>>> connection between the nodes.
>>>> Has the cluster been working with the 3 nodes before?
>>>> Klaus
>>> Hi Klaus
>>> Yes it has been working before with all 3 nodes and migrations back
>>> and forth, but a few more VirtualDomains have been deployed since the
>>> last migration test.
>>> It happens very fast, almost immediately after migration is starting.
>>> Could it be that some timeout values should be adjusted ?
>>> I just don't have any idea where to start looking, as to me there is
>>> nothing obviously suspicious found in the logs.
>> I would look at performance stats, may be node02 was overloaded and
>> could not answer in time. Although standard sar stats are collected
>> every 15 minutes which is usually too coarse for it.
>> Migration could stress network. Talk with your network support, any
>> errors around this time?
> I see no network errors around that time when checking e-mails and
> syslogs from network equipment.
> Last night I tried to bring up the node02 that was fenced earlier 'pcs
> cluster start', and initiated a migration. Same thing happened, node03
> was fenced almost immediately.
> Then I tried to bring back up node03 and leave it for the night. This
> morning I then did several migrations successfully. So it might be
> something that needs more time to get up, maybe the
> clustermanaged-libvirtd network components.
Did you - instead of migrating - try to stop the vm on one node and
bring it up on the other? Just to see if it is the traffic or the vm
alonein that state ... maybe starting the vm already does something
harmful to networking if libvirtd didn't have the time to bring
up the networking topology (or something similar during startup
like it being attached somewhere wrong - missing the right attachment
point still - so that it grabs all packets ...).
When doing a migration you are possibly moving a mac-address from
one switch-port to another. Maybe bringing up the network topology
is doing some testing/gratuitous arp with the same mac which looks
like the one more switching around - within a certain time - that
the switch is configured to punish with a temporary locking of the
Just a few unsorted thoughts ... at least nothing that would ring a
bell immediately ...

> I have Prometheus scraping node_exporter from all 3 nodes, and I can
> dig around network traffic around the incidents, for the 2 failing
> incidents, upon migration the traffic rises to a stable 250Mb/s or
> 600Mb/s for a couple of minutes.
> For successful migrations, network traffic always goes to 1000Mb/s
> which is the max for single connection, the nodes have 4x1000Mb nics
> bonded, and there is very low traffic going on there around any of the
> incidents
> /Steffen

More information about the Users mailing list