Administering HDFS
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Decommissioning slave nodes

Hadoop provides the decommission feature to retire a set of existing slave nodes (DataNodes, NodeManagers, or HBase RegionServers) in order to prevent data loss.

Slaves nodes are frequently decommissioned for maintenance. As a Hadoop administrator, you will decommission the slave nodes periodically in order to either reduce the cluster size or to gracefully remove dying nodes.