title: cassandra multi datacenter data sync lag
body: <p>I have configured a Cassandra cluster spanning two data centers (AWS, us-east and us-west). The writes happen only to the us-east ring, and I can see the data synchronizing to the other ring. However, the lag is high. </p>
  
  <pre><code>On DC1
  cqlsh:ks&gt; select count(*) from cf1 limit 1000000;
  
   count
  --------
   225568
  
  On DC2
  cqlsh:ks&gt; select count(*) from cf1 limit 1000000;
  
   count
  --------
   139964
  </code></pre>
  
  <p>--</p>
  
  <ol>
  <li>Why is this so, and what does this depend on?</li>
  <li>is there a way to see the lag using any tools? is this available to view in OpsCenter?</li>
  </ol>