The idea of the upgrade is: drain the workloads and take the traffic off, then upgrade the control plane nodes first and the worker nodes afterwards. 1. Check the cluster version 1 2 3 4 kubectl version Client Version: version.Info{Major:"1", Minor:"20", GitVersion:"v1.20.4", GitCommit:"e87da0bd6e03ec3fea7933c4b5263d151aafd07c", GitTreeState:"clean", BuildDate:"2021-02-18T16:12:00Z", GoVersion:"go1.15.8", Compiler:"gc", Platform:"linux/amd64"} Server Version: version.

Judging from the survey data, more people lean toward choosing small clusters. Below is a comparison list from the perspective of node count and node configuration. Below is a comparison of choosing a few large clusters versus many small clusters: Feature A few large clusters Many small clusters Resource utilization High Low Node management overhead Low High Resource scaling range Large Small Resource scheduling range Large Small Efficiency of inter-application communication High Low Cluster operations difficulty High Low Cluster version diversity Low High Blast radius Large Small Below is a comparison of choosing a few high-spec nodes versus many low-spec nodes:

1. Basic Introduction to Etcd Etcd is a distributed Key/Value storage system. Through distributed locks, leader election, and write barriers it achieves distributed coordination, offering highly available, persistent data storage and retrieval services. How it works Every Etcd node stores a complete copy of the data, and at any moment

1. Introduction to Velero Velero is an open-source Kubernetes cluster backup and migration tool from the heptio team (acquired by VMWare). Velero stores cluster resources in object storage. It supports AWS, Azure, and GCP object storage by default, is compatible with the S3 protocol, and can be extended to other platforms such as Aliyun OSS through plugins.

1. Cluster Planning Prepare three hosts: one Master and two Nodes. Operating system: CentOS 7 Specs: 2 Core 4 GB Docker version: 18.06.3 Kubernetes version: 1.15.3 If you are using a purchased cloud host, open the following ports: 1 2 3 4 5 6 7 8 9 10 11 12