title: logstash could not be started when running multiple instances - path.data setting
body: <p>Hi i am new to the internals of ELK stack</p>
  
  <p>running a logstash process in background, and when it got picked up the matching file pattern, it says as in below</p>
  
  <p>i want to understand here what is the importance of <code>path.data</code> option, Please help me out</p>
  
  <pre><code>[FATAL][logstash.runner] Logstash could not be started because there is already another instance using the configured data directory. If you wish to run multiple instances, you must change the "path.data" setting.
  </code></pre>