title: Postgresql I/O utilization
body: <p>Newrelic shows I/O pikes of up to 100% reads. </p>
  
  <p><a href="https://i.stack.imgur.com/3fUUN.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/3fUUN.png" alt="enter image description here"></a> </p>
  
  <p>The rest of the time it's close to 0.</p>
  
  <p>It doesn't coincide in time with our cron jobs (database backup, analyze, etc.), also almost no match with autovacuum (pg_stat_all_tables.last_autovacuum).</p>
  
  <p>Querying pg_stat_activity also shows nothing but our simple queries sent by Ruby application</p>
  
  <pre><code>select * 
  from pg_stat_activity 
  where query_start between '2017-09-25 09:00:00' and '2017-09-25 11:00:00';
  </code></pre>
  
  <p>And these queries are not even among our slow queries in log file.</p>
  
  <p>Please advise how to identify what processes cause such I/O load.</p>