将硬盘挂载到指定目录，如/data
在hdfs-site.xml中修改
<property>
<name>dfs.datanode.data.dir</name>
<value>file://${hadoop.tmp.dir}/dfs/data,/data</value>
<description>Determines where on the local filesystem an DFS data node
should store its blocks. If this is a comma-delimited
list of directories, then data will be stored in all named
directories, typically on different devices.
Directories that do not exist are ignored.
</description>
</property>
重启集群
原文：http://www.cnblogs.com/qhg1/p/4329701.html