Proxmox HA - 50% nodes online quorum

[krzysiexp]

Hi!
I have 4 nodes cluster.
I want to have a quorum when two of them are offline.
I tried setting auto_tie_breaker in corosync.conf and corosync-quorumtool -e 2 but both methods didin't work.
How to configure that?
And another question, why changing corosync.conf after creating cluster with pve-command tools is not safe and how to change config of this service in the right way?
Yes, I know that when cluster is created from 4 nodes you should have at least 3 nodes to quorum.

 

[Klaus Steinberger]

Sure you will not like to have a 50% quorum. That will give you split brain problems. Split brain will lead to VM's running twice and destroying their images, so don't do it. Don't ever think about a 50% quorum.

you can setup for example a fifth node on a small box just as an quorum node. Even a Raspberry would do for that, as long as you exclude it from HA Groups.

 

[krzysiexp]

Ok, I understand this.
Is there any way else to have a quorum without additional Proxmox node? For example will fencing with cisco switch do the job?

 

[Klaus Steinberger]

Not yet as I know

 

[wolfgang]

You need even quorum to use a fence device like a cisco switch quorum.

 

[krzysiexp]

You need even quorum to use a fence device like a cisco switch quorum.

So in conclusion: it can't be done without additional Proxmox node?

 

[wolfgang]

So in conclusion: it can't be done without additional Proxmox node?

Correct.
You can alternative use a corosync qdevice this is a daemon what act as a tiebreaker.
see
https://github.com/corosync/corosync-qdevice