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).

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*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 *

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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 [image: THG Ingenuity Logo] https://www.thg.com https://www.linkedin.com/company/thgplc/?originalSubdomain=uk https://twitter.com/thgplc?lang=en