title: Is there any side effect of increasing file_cache_size_in_mb?
body: <p>I use cassandra 3.9, but <code>outOfMemoryError</code> happens often and each nodes has been down one by one.<br>
  I'm making a research about configuration, and I think one of the way is to increase <code>file_cache_size_in_mb</code>. Current size is 512MB.<br>
  But I'm not an expert of memory usage, and anxious about side effect to performance. I think disk cache will be cut off and cassandra's I/O performance is slowed down a little.<br>
  Do you know any other points I should be aware?  </p>
  
  <p>My machine spec is:   </p>
  
  <ul>
  <li>machine memory is 128GB. Java heap is 8GB.</li>
  <li>Right now only 18GB is used, but another 100GB is allocated for OS disk cache. Totally free memory is about 1GB.</li>
  <li>No other process except cassandra.</li>
  </ul>