[ClusterLabs] Can a two node cluster start with only one node?

[Ken Gaillot]

On Wed, 2022-04-20 at 12:09 -0400, john tillman wrote:
> Here's the scenario:
>    I have a two node cluster setup. (details to follow)
>    I start with both nodes booted.
>    I can reboot the active node and the resources move.
> 

By default, corosync's two_node mode enables wait_for_all, which means
that when a node first starts up, it has to see the other node at least
once before it will claim to have quorum. This is the only safe mode of
operation, otherwise two nodes that get severed from each other and
then reboot will both claim quorum.

However you can override that by setting wait_for_all to false in the
corosync configuration. This is mainly useful when you are
intentionally and manually bringing the cluster down and want to bring
up a single node. Once the node is up you can set wait_for_all back to
true for safety, so if it reboots unexpectedly it will require manual
intervention again to get going.
-- 
Ken Gaillot <kgaillot at redhat.com>