Category Archives: HDFS

Configuration Parameters: What can you just ignore?

Categories: General Hadoop HDFS MapReduce

Configuring a Hadoop cluster is something akin to voodoo. There are a large number of variables in hadoop-default.xml that you can override in hadoop-site.xml. Some specify file paths on your system, but others adjust levers and knobs deep inside Hadoop’s guts. Unfortuately, there’s little or no documentation on how to set them well. Is there a single optimal configuration? Are there some settings that can just be “set to 11?”

Nigel's guitar goes to 11, but your cluster might not. At Cloudera,

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Multi-host SecondaryNameNode Configuration

Categories: Hadoop HDFS

You might think that the SecondaryNameNode is a hot backup daemon for the NameNode. You’d be wrong. The SecondaryNameNode is a poorly understood component of the HDFS architecture, but one which provides the important function of lowering NameNode restart time. This blog post describes how to configure this daemon in a large-scale environment. The default Hadoop configuration places an instance of the SecondaryNameNode on the same node as the NameNode. A more scalable configuration involves configuring the SecondaryNameNode on a different machine.

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