Good day,
Thank you for reaching us!
As its is stated in the documentation, an upgrade process consist of the following:
- Add a new buffer node (or as many nodes as configured in max surge) to the cluster that runs the specified Kubernetes version.
- Cordon and drain one of the old nodes to minimize disruption to running applications. If you're using max surge, it will cordon and drain as many nodes at the same time as the number of buffer nodes specified.
- When the old node is fully drained, it will be reimaged to receive the new version, and it will become the buffer node for the following node to be upgraded.
- This process repeats until all nodes in the cluster have been upgraded.
- At the end of the process, the last buffer node will be deleted, maintaining the existing agent node count and zone balance.
- You can also customize a node surge upgrade depending on the requirements/need you might have: a faster upgrade with a downtime(maybe for testing environments) or a 33% max surge recommended for production environments.
- If you stick with the recommended option for production, there won't be a noticeable downtime for your applications.
You can refer to this document as well for more information and examples:
Please let us know if you have any further questions and we will be glad to assist you further. Thank you!
Please "Accept as Answer" and Upvote if it helped, so that it can help others in the community looking for help on similar topics.