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How to recover the data of decommisioned node.

How to recover the decommissioning node's data. What actually happens with the data. Is it necessary to run hadoop balancer command, for start getting replicate the data into the other nodes for make the configured replication factor for each file.

1 REPLY 1

Super Mentor

@Rahul Gupta

The following doc describes the full procedure of DataNode Decommission and the events that happens during the Decommission.

https://docs.hortonworks.com/HDPDocuments/HDP2/HDP-2.6.1/bk_administration/content/ref-a179736c-eb7c...

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When all the DataNodes report their state as Decommissioned (on the DataNodes page, or on the Decommissioned Nodes page at http://<NameNode_FQDN>:8088/cluster/ nodes/decommissioned), all of the blocks have been replicated. You can then shut down the decommissioned nodes.

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Regarding the HDFS rebalancer, which is a tool for balancing data across the storage devices of an HDFS cluster. It is recommended to run the HDFS balancer periodically during times when the cluster load is expected to be lower than usual. https://docs.hortonworks.com/HDPDocuments/HDP2/HDP-2.6.0/bk_hdfs-administration/content/overview_hdf...

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Later once you do recovery of the decomissioned node it is better to perform the hdfs rebalancing.

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