Upgrading Nodes Manually

[ShunsukeMiyake]

I would like to know more about "Upgrading Nodes Manually" as described in the following document: https://rke.docs.rancher.com/upgrades#upgrading-nodes-manually

We are considering upgrading the Kubernetes version of our downstream cluster.
Could you advise on how we could initiate the upgrade to manually upgrade each node one at a time?

Our company uses Rancher to manage our clusters.
Since the target cluster for the upgrade was set up using Rancher's UI, we have access to the configuration (cluster.yaml) via the Rancher UI.
If we change the Kubernetes version in this configuration, the upgrade for each node would likely start automatically.

However, since we would like to upgrade each node manually, we are thinking of setting the following options as shown below.
Would this allow us to perform each node's upgrade manually?

• Drain nodes -> false
• Maximum Worker Nodes Unavailable -> 0

For example, within the cluster, we have Redis, with the master and slave located on separate nodes.
When the master begins upgrading, I believe it will take a certain amount of time for the slave to detect that it can no longer communicate with the master.
During this period, data cannot be recorded to the master, leading to a potential data loss for that time span.
To minimize data loss, we would like to control the order and timing of the upgrade—for instance, by starting the upgrade from the slave.

Thank you for reading.