title: Cassandra Storage: which read is faster?
body: <p>I have two ways of storing data</p>
  
  <p>Use case:
  Storing incoming data for each product</p>
  
  <p>1) <code>CREATE COLUMN FAMILY product_data WITH comparator = TimeUUIDType AND    key_validation_class=UTF8Type AND default_validation_class = UTF8Type;</code></p>
  
  <p>This will store data like</p>
  
  <pre><code>product_id|timeuuid1     | timeuuid2      |
  A         | (some-value) |  (some-value)  |
  </code></pre>
  
  <p>2) <code>CREATE COLUMN FAMILY product_data(product_id varchar, time TIMESTAMP, some-data varchar, key(product_id, time))</code></p>
  
  <p>Now my aim is to have better disk reads. In first case entire row is at same place so disk reads are fast for all time range reads. In second case data for one product will be in same replicas but will they be in same disk space?</p>