Cluster Rolling Upgrade : Necessary to disable replica shard allocation for each node?

Hello Elasticers,

I'm asking if it's really necessary to disable replica shard allocation for each node as described in the documentation

As this is a cluster setting, why not disable replica shard allocation one time, upgrade all nodes and then re-enable replicas shard allocation at the end ?

Thanks for your feedback ! :slight_smile:

You should re-enable it and allow the cluster to recover to green health after each node if possible. If you do not, your cluster health may end up red (i.e. some shards are completely unavailable) during the process, which rather defeats the purpose of doing a rolling upgrade.

Ok. So very few chances that someting like that arrive but as this is possible, it's recommended to do it for each node to reduce the risk.

That sounds logic. Thanks @DavidTurner

I think it's pretty likely to be honest, unless you have stopped all write traffic for the duration of the upgrade. Again, this rather defeats the purpose of doing a rolling upgrade.