What are the effects of rolling updates?

When you apply rolling updates to the TiDB services, the running application is affected to varying degrees. Therefore, it is not recommended that you perform a rolling update during business peak hours. You need to configure the minimum cluster topology (TiDB * 2, PD * 3, TiKV * 3). If the Pump or Drainer service is involved in the cluster, it is recommended to stop Drainer before rolling updates. When you upgrade TiDB, Pump is also upgraded.