ES rolling upgrade from 6.3.2 to 6.8.22, ES plug-in version should be upgraded to 6.8.22?

[qiuxb (qiuxinbo)]

ES is upgraded from version 6.3.2 to 6.8.22 in a rolling manner. After the upgrade, the cluster status is abnormal. How to roll back to 6.3.2?

Thanks for the reply, I have a question about rolling upgrades, the part marked in the following text, is it understood that it is not allowed to accept multiple ES versions for a long time during the upgrade? However, the actual rolling upgrade requires a gradual upgrade of nodes one by one, and needs to wait for the node status to recover and the cluster status to recover to green, which may take a long time. During this period, two versions of ES must exist in the cluster at the same time. R…

I still have a question, what are the main factors that affect the coexistence of multiple versions of ES during ES rolling upgrades? Why is it safer to be under the hour?