title: capistrano, :db role, what's it for?
body: <p>As far as I can tell, the capistrano <code>:db</code> role is used only to run migrations. </p>
  
  <p>(Thus, in most cases it probably <em>shouldn't</em> actually be the server that runs your database. Why would you have a ruby/rails stack there (or allow ssh logins there)? it's just whatever server you want to actually execute the rails migrations). </p>
  
  <p>And only the server identified as db role with <code>:primary =&gt; true</code> is used to run migrations. </p>
  
  <p>So any other servers identified as 'db' role but without <code>:primary =&gt; true</code>... are used for nothing at all? So why does the default deploy.rb created by <code>capify .</code> encourage you to list them?  What would you even list here?</p>
  
  <p>Anything I'm missing?</p>