Steps to upgrade:
- Sanitarium hosts on both DCs (already done https://phabricator.wikimedia.org/T275112 https://phabricator.wikimedia.org/T272008)
- Sanitarium masters on both DCs (https://phabricator.wikimedia.org/T280492) - ensure sanitarium replicates from a 10.4 host.
- Available backup source on the standby DC db2101 (to be confirmed by @jcrespo)
- Candidate master on the standby DC
- Master on the standby DC
- Switchover backup generation standby DC (to be coordinated/confirmed with @jcrespo) https://gerrit.wikimedia.org/r/c/operations/puppet/+/693142
- Candidate master on the primary DC
- Available backup source on the primary DC db1150 (to be confirmed by @jcrespo)
- Switchover on the primary DC to promote a Buster+10.4 host to master: T284529
- Switchover backup generation Primary DC https://gerrit.wikimedia.org/r/c/operations/puppet/+/698157
- Upgrade the old master and make it a candidate master.
- Add s5 to orchestrator
- Cleanup (remove) old backup sources from both DCs
Please read the doc about procedure for more details.