Need suggestion to stop or Decommission Datanode?

Question

Hi , We are using 12 Datanodes in our cluster. And we have 3 replication factor.

Currently we are doing cost optimization and our total cluster is 35% used. We want to remove one datanode from our cluster, but we want to see first how our cluster performs on 11 datanodes. if it doesn't perform well, we need to restart that datanode again.

To experiment this- Do I need to Stop the datanode or Decomission datanode?

Please need suggestion.

Shelton · Accepted Answer

@Madhura Mhatre It's well documented in by hortonworks  Once you launch the decommissioning the blocks on that node  will be distributed to the other node remaining nodesIf the replication factor is higher than the number of existing data nodes after the removal, the removal process is not going to succeed!

Shelton · Answer

@Madhura Mhatre Surely you could just t^do that but what happens to the replicas stored on that particular data node? Somehow your cluster has to reconstruct those replicas if you had a replicator factor of more than 1. Here I was talking about planned maintenance! Just switching it off will also force your cluster to do the same thing in the background with alerts and ONLY when the replicas have been reconstructed will those alerts go away.There is a performance cost for both decommissioning and just unplugging the data node.

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