title: Deploy Spark on multiple subnets on EC2
body: <p>I want to deploy spark on EC2 using <code>spark-ec2</code> tool. The target environment is a private VPC spanned over 3 availability zone. I see from the docs that I can distribute my instances over AZs by adding <code>--zone=all</code> but it's not the same for <code>--subnet-id</code> param because it only accepts one input.</p>
  
  <p>How can I introduce more that one subnets to the tool? Is it possible at all?</p>