@JSSSS The error is this "java.io.IOException: File /user/JS/input/DIC.txt._COPYING_ could only be written to 0 of the 1 minReplication nodes. There are 3 datanode(s) running and 3 node(s) are excluded in this operation." All the 3 datanode according to the log are excludeNodes=[192.168.1.81:9866, 192.168.1.125:9866, 192.168.1.8> with replication factor of 3 , writes should succeed to all the 3 datanodes else the write fails. The cluster may have under-replicated or unavailable blocks due to excluded nodes HDFS cannot use these nodes, possibly due to: Disk space issues. Write errors or disk failures. Network connectivity problems between the NameNode and DataNodes. 1. Verify if the DataNodes are live and connected to the NameNode hdfs dfsadmin -report Look for the "Live nodes" and "Dead nodes" section If all 3 DataNodes are excluded, they might show up as dead or decommissioned. Ensure the DataNodes have sufficient disk space for the write operation df -h Look at the HDFS data directories (/hadoop/hdfs/data) If disk space is full, clear unnecessary files or increase disk capacity hdfs dfs -rm -r /path/to/old/unused/files View the list of excluded nodes cat $HADOOP_HOME/etc/hadoop/datanodes.exclude If nodes are wrongly excluded: Remove their entries from datanodes.exclude. Refresh the NameNode to apply changes hdfs dfsadmin -refreshNodes Block Placement Policy: If the cluster has DataNodes with specific restrictions (e.g., rack awareness), verify the block placement policy grep dfs.block.replicator.classname $HADOOP_HOME/etc/hadoop/hdfs-site.xml Default: org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault Happy hadooping
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