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Configuring HDFS block size
Getting ready
To step through the recipes in this chapter, make sure you have completed the recipes in Chapter 1, Hadoop Architecture and Deployment or at least understand the basic Hadoop cluster setup.
How to do it...
sshto the master node, which is Namenode, and navigate to the directory where Hadoop is installed. In the previous chapter, Hadoop was installed at/opt/cluster/hadoop:$ ssh root@10.0.0.4- Change to the
Hadoopuser, or any other user that is running Hadoop, by using the following:$ sudo su - hadoop - Edit the
hdfs-site.xmlfile and modify the parameter to reflect the changes, as shown in the following screenshot:
dfs.blocksizeis the parameter that decides on the value of the HDFS block size. The unit is bytes and the default value is 64 MB in Hadoop 1 and 128 MB in Hadoop 2. The block size can be configured according to the need.- Once the changes are made to
hdfs-site.xml, copy the file across all nodes in the cluster. - Then restart the Namenode and
datanodedaemons on all nodes. - The block size can be configured per file by specifying it during the copy process, as shown in the following screenshot:
How it works...
The best practice is to keep the configurations the same across all nodes in the cluster, but it is not mandatory. For example, the block size of Namenode can be different from that of the edge node. In that case, the parameters on the source node will be effective. It means that the parameter on the node from which the copying is done will be in effect.