Change the Hadoop configuration in accordance with the changes made to the number of slave servers.
Make these changes on the primary master server, the secondary master server, slave servers, and development servers.
Edit /etc/hadoop/mapred-site.xml, and reconfigure the value in the mapred.reduce.tasks property.
See
Refer to "C.3 mapred-site.xml" for information on properties configured in mapred-site.xml.
