Debian 7 + MySQL 5.5 to Debian 9/10 + MySQL 8

Just looking for high-level feedback to make sure I’m starting in the right direction. We currently have a multi-site cluster running Deb 7 with Percona 5.5. Our plan is to upgrade to Deb 9 (possibly 10) and it would seem to make the most sense to go to Percona 8

In my mind, my simple solution is to simply build new Deb 9 + Percona 8 nodes and join them to the cluster. Let SST do it’s magic and then remove the old nodes from the cluster. Old DB nodes: “server1”, “server2”, “server3” and new DB nodes: “server4”, “server5”, “server6”.

Sounds easy… Might it actually work?

I’d probably want to rename the Deb 9 + Percona 8 servers to “server1”, “server2”, “server3”.

Hi Marco.Shaw

This won’t work for replication. I have been looking for some blog posts that will help you to piece together a strategy.

First of all, you should test your application queries. The optimizer changes substantially between major version upgrades and you can anticipate some big differences. You can use pt-upgrade from Percona Toolkit to help with that.

pt-query-digest could also pay dividends here.

This old post gives an outline of the kind of things you need to consider https://www.percona.com/blog/2014/09/19/mysql-upgrade-best-practices/ and covers replication in some part.
And this may be a useful read too https://www.percona.com/blog/2014/11/04/data-inconsistencies-on-mysql-replicas-beyond-pt-table-checksum/

You’ll need a back out (back up) strategy too, in case of a failed upgrade. If those don’t help clarify, don’t hesitate to come back and I’ll see if I can get further insight for you.