title: Cassandra terrible performance on select
body: <p>I have two nodes Cassandra cluster. In order to test Cassandra i built a File table (Fid Integer,Sid Integer), Which Fid is key. I built index on Sid, Insert rate is about 10,000 in 1 second. But when i select from table the performance is terrible, and for low limit like 1000 it generate error, bellow is my sample code,</p>
  
  <pre><code>from cassandra.cluster import Cluster
  
  cluster = Cluster(['127.0.0.1'])
  session = cluster.connect('myk')
  rows = session.execute('SELECT * FROM File WHERE sid = 1 limit 1000')
  for user_row in rows:
      print user_row
  </code></pre>
  
  <p>Error message is:</p>
  
  <pre><code>Traceback (most recent call last):
    File "Test.py", line 5, in &lt;module&gt;
      rows = session.execute('SELECT * FROM File WHERE sid = 1 limit 1000')
    File "build\bdist.win32\egg\cassandra\cluster.py", line 1065, in execute
    File "build\bdist.win32\egg\cassandra\cluster.py", line 2427, in result
  cassandra.OperationTimedOut: errors={}, last_host=172.16.47.130
  </code></pre>
  
  <p>by changing </p>
  
  <pre><code>rows = session.execute('SELECT * FROM File WHERE sid = 1 limit 1000')
  </code></pre>
  
  <p>to </p>
  
  <pre><code>rows = session.execute('SELECT * FROM File WHERE sid = 1 limit 1000',timeout=20.0)
  </code></pre>
  
  <p>Error has gone, but why performance (for fetching 1000 rows from a 800,000 records table) is very slow? Any hints?</p>