[PVE-User] PVE 6.2 Strange cluster node fence

Stefan M. Radman smr at kmi.com
Wed Apr 14 15:57:09 CEST 2021 

Hi Eneko

That’s a nice setup and I bet it works well but you should do some hand-tuning to increase resilience.

Are the unused eno1 and eno2 interfaces on-board 1GbE copper interfaces?

If that’s the case I’d strongly recommend to turn them into dedicated untagged interfaces for the cluster traffic, running on two separate “rings".

https://pve.proxmox.com/wiki/Separate_Cluster_Network
https://pve.proxmox.com/wiki/Separate_Cluster_Network#Redundant_Ring_Protocol

Create two corosync rings, using isolated VLANs on your two switches e.g. VLAN4001 on Switch1 and VLAN4002 on Switch2.

eno1 => Switch1 => VLAN4001
eno2 => Switch2 => VLAN4002

Restrict VLAN4001 to the access ports where the eno1 interfaces are connected. Prune VLAN4001 from ALL trunks.
Restrict VLAN4001 to the access ports where the eno2 interfaces are connected. Prune VLAN4002 from ALL trunks.

Assign the eno1 and eno2 interfaces to two separate subnets and you are done.

With separate rings you don’t even have to stop your cluster while migrating corosync to the new subnets.
Just do them one-by-one.

With corosync running on two separate rings isolated from the rest of your network you should not see any further node fencing.

Stefan

On Apr 14, 2021, at 15:18, Eneko Lacunza <elacunza at binovo.es<mailto:elacunza at binovo.es>> wrote:

Hi Stefan,

El 14/4/21 a las 13:22, Stefan M. Radman escribió:
Hi Eneko

Do you have separate physical interfaces for the cluster (corosync) traffic?
No.
Do you have them on separate VLANs on your switches?
Onyl Ceph traffic is on VLAN91, the rest is untagged.

Are you running 1 or 2 corosync rings?
This is standard... no hand tuning:

nodelist {
  node {
    name: proxmox1
    nodeid: 2
    quorum_votes: 1
    ring0_addr: 192.168.90.11
  }
  node {
    name: proxmox2
    nodeid: 1
    quorum_votes: 1
    ring0_addr: 192.168.90.12
  }
  node {
    name: proxmox3
    nodeid: 3
    quorum_votes: 1
    ring0_addr: 192.168.90.13
  }
}

quorum {
  provider: corosync_votequorum
}

totem {
  cluster_name: CLUSTERNAME
  config_version: 3
  interface {
    linknumber: 0
  }
  ip_version: ipv4-6
  secauth: on
  version: 2
}


Please post your /etc/network/interfaces and explain which interface connects where.
auto lo
iface lo inet loopback

iface ens2f0np0 inet manual
# Switch2

iface ens2f1np1 inet manual
# Switch1

iface eno1 inet manual

iface eno2 inet manual

auto bond0
iface bond0 inet manual
    bond-slaves ens2f0np0 ens2f1np1
    bond-miimon 100
    bond-mode active-backup
    bond-primary ens2f0np1

auto bond0.91
iface bond0.91 inet static
    address 192.168.91.11
#Ceph

auto vmbr0
iface vmbr0 inet static
    address 192.168.90.11
    gateway 192.168.90.1
    bridge-ports bond0
    bridge-stp off
    bridge-fd 0

Thanks

Thanks

Stefan


On Apr 14, 2021, at 12:12, Eneko Lacunza via pve-user <pve-user at lists.proxmox.com<mailto:pve-user at lists.proxmox.com>> wrote:


From: Eneko Lacunza <elacunza at binovo.es<mailto:elacunza at binovo.es>>
Subject: Re: [PVE-User] PVE 6.2 Strange cluster node fence
Date: April 14, 2021 at 12:12:09 GMT+2
To: pve-user at lists.proxmox.com<mailto:pve-user at lists.proxmox.com>


Hi Michael,

El 14/4/21 a las 11:21, Michael Rasmussen via pve-user escribió:
On Wed, 14 Apr 2021 11:04:10 +0200
Eneko Lacunza via pve-user<pve-user at lists.proxmox.com<mailto:pve-user at lists.proxmox.com>>  wrote:

Hi all,

Yesterday we had a strange fence happen in a PVE 6.2 cluster.

Cluster has 3 nodes (proxmox1, proxmox2, proxmox3) and has been
operating normally for a year. Last update was on January 21st 2021.
Storage is Ceph and nodes are connected to the same network switch
with active-pasive bonds.

proxmox1 was fenced and automatically rebooted, then everything
recovered. HA restarted VMs in other nodes too.

proxmox1 syslog: (no network link issues reported at device level)
I have seen this occasionally and every time the cause was high network
load/network congestion which caused token timeout. The default token
timeout in corosync IMHO is very optimistically configured to 1000 ms
so I have changed this setting to 5000 ms and after I have done this I
have never seen fencing happening caused by network load/network
congestion again. You could try this and see if that helps you.

PS. my cluster communication is on a dedicated gb bonded vlan.
Thanks for the info. In this case network is 10Gbit (I see I didn't include this info) but only for proxmox nodes:

- We have 2 Dell N1124T 24x1Gbit 4xSFP+ switches
- Both switches are interconnected with a SFP+ DAC
- Active-passive Bonds in each proxmox node go one SFP+ interface on each switch. Primary interfaces are configured to be on the same switch.
- Connectivity to the LAN is done with 1 Gbit link
- Proxmox 2x10G Bond is used for VM networking and Ceph public/private networks.

I wouldn't expect high network load/congestion because it's on an internal LAN, with 1Gbit clients. No Ceph issues/backfilling were ocurring during the fence.

Network cards are Broadcom.

Thanks

Eneko Lacunza
Zuzendari teknikoa | Director técnico
Binovo IT Human Project

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