Ensure all services in the cluster are running.

Run each Service Check (found under the Service Actions menu) and confirm they execute successfully.

Clear all alerts, or understand why they are being generated. Remediate as necessary.

Confirm start and stop for all services are executing successfully.

Time service start and stops. The time to start and stop services is a big contributor to overall upgrade time so having this information handy is useful.

If you are using a local repository, download the software packages prior to the upgrade. Place them in a local repository and/or consider using a storage proxy since multi-gigabyte downloads is required on all nodes in the cluster.

Ensure point-in-time backups are taken of all DBs supporting the clusters. This includes Ambari and Ranger databases.