title: Role of master in Spark standalone cluster
body: <p>In a Spark standalone cluster, what is exactly the role of the master (a node started with start_master.sh script)?</p>
  
  <p>I understand that is the node that receives the jobs from the submit-job.sh script, but what is its role when processing a job?</p>
  
  <p>I'm seeing in the web UI that always delivers the job to a slave (a node started with start_slave.sh) and is not participating from processing, Am I right? In that case, should I also run also the script start_slave.sh in the same machine than master to to take advantage of its resources (cpu and memory)?</p>
  
  <p>Thanks in advance.</p>