There are many tools out there that can help you diagnose problems with Solr. You can monitor your operating system by yourself by using different operating system commands such as
iostat. You can use different Java tools such as
jvisualvm to look at the JMX mbeans, you can monitor your garbage collector work, and so on. However in order to properly diagnose what's happening with your Apache Solr cluster you'll need to see the whole view as well as the specifics. There are different tools out there that you can use, however this recipe will show you what you can find in one of them—Scalable Performance Monitoring.
This recipe assumes that you have Scalable Performance Monitoring ...