Comments - Is it possible to downgrade a Galera clusternode to a slightly older version and rejoin the cluster?
Content reproduced on this site is the property of its respective owners,
and this content is not reviewed in advance by MariaDB. The views, information and opinions
expressed by this content do not necessarily represent those of MariaDB or any other party.
That should be fine, as long as there were no changes between MariaDB 10.2.9 and MariaDB 10.2.18 that broke backward compatibility. I took a quick look through the release notes for all of the releases between those versions, and I didn't see any.
However, I believe that MariaDB 10.2.19 did introduce a backward incompatible change with the new redo log changes that are tied to
innodb_safe_truncate
. It sounds like you aren't actually using MariaDB 10.2.19 though.