[ClusterLabs] corosync 2.4 and 3.0 in one cluster.

[Ken Gaillot]

On Fri, 2023-09-01 at 17:56 +0300, Мельник Антон wrote:
> Hello,
> 
> I have a cluster with two nodes with corosync version 2.4 installed
> there.
> I need to upgrade to corosync version 3.0 without shutting down the
> cluster.

Hi,

It's not possible for Corosync 2 and 3 nodes to form a cluster. They're
"wire-incompatible".

> I thought to do it in this way:
> 1. Stop HA on the first node, do upgrade to newer version of Linux
> with upgrade corosync, change corosync config.
> 2. Start upgraded node and migrate resources there.
> 3. Do upgrade on the second node.

You could still do something similar if you use two separate clusters.
You'd remove the first node from the cluster configuration (Corosync
and Pacemaker) before shutting it down, and create a new cluster on it
after upgrading. The new cluster would have itself as the only node,
and all resources would be disabled, but otherwise it would be
identical. Then you could manually migrate resources by disabling them
on the second node and enabling them on the first.

You could even automate it using booth. To migrate the resources, you'd
just have to reassign the ticket.

> Currently on version 2.4 corosync is configured with udpu transport
> and crypto_hash set to sha256.
> As far as I know version 3.0 does not support udpu with configured
> options crypto_hash and crypto_cipher.
> The question is how to allow communication between corosync instances
> with version 2 and 3, if corosync version 2 is configured with
> crypto_hash sha256.
> 
> 
> Thanks,
> Anton.
-- 
Ken Gaillot <kgaillot at redhat.com>