The document discusses developing a comprehensive monitoring approach for Hadoop clusters. It recommends starting with basic monitoring of nodes using Nagios and Cacti for metrics like CPU usage, disk usage, and network traffic. Additional Hadoop-specific checks and graphs are added like checking DataNodes and monitoring the NameNode via JMX. JMX is also used to create alarms in Nagios based on metrics like number of files. The approach emphasizes starting simply and gradually expanding monitoring as the cluster grows.