Datanode
This lesson explains the role of Datanode in HDFS.
DataNodes
The Datanode stores the actual data. It stores the data blocks on its local filesystem and sends a block report to the Namenode.
The data for HDFS files will be stored in the directory specified as the value for the configuration setting dfs.datanode.data.dir
. The default value of this setting is ${hadoop.tmp.dir}/dfs/data
. In our terminal setup the data directory is located at usr/local/tmp/dfs/data/
. We’ll upload a file to HDFS containing a string; the corresponding data is written to the local disk of the DataNode. Execute the commands in the terminal and examine the outcome. A screen-shot of the directory with the data appears below:
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