Just to complement Danny's comment: this applies to any kind of distributed cluster; if you have an even number of members or only one member in a cluster that requires a quorum to work, you will be prone to a split-brain situation. So it's not safe for production.

https://en.wikipedia.org/wiki/Split-brain_(computing)

Cheers!

On Thu, Mar 16, 2023 at 12:12 PM Danny Webb <Danny.Webb@thehutgroup.com> wrote:

You can't do 2 control nodes with kolla as you need an odd number of mariadb nodes for quorum purposes (1 or 3 or more).

From: kaqiu pi <thremes172@gmail.com>
Sent: 16 March 2023 17:05
To: openstack-discuss@lists.openstack.org <openstack-discuss@lists.openstack.org>
Subject: Fwd: [kolla-ansible] Whether the cluster of two control nodes is available

CAUTION: This email originates from outside THG

Hi，

I'm a newer in kolla-ansibe. And I could deploy a cluster of two controll nodes by kolla-ansible. But I don't konw whether the cluster is anvailable?

I would like to ask, when the number of control nodes is 2, the status of mariadb and rabbitmq clusters, are they safe and available for production?

Thanks for any guidance.

Good Luck

Danny Webb

Principal OpenStack Engineer

Danny.Webb@thehutgroup.com

Alvaro Soto

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