title: Cassandra storage vs memory sizing
body: <p>I am considering developing an application with a Cassandra backend. I am hoping that I will be able to run each cassandra node on commodity hardware with the following specs: </p>
  
  <ul>
  <li>Quad Core 2GHz i7 CPU</li>
  <li>2x 750GB disk drives</li>
  <li>16 GB installed RAM</li>
  </ul>
  
  <p>Now, I have been reading online that the available disk-space for Cassandra should be double the amount that is stored on the disks, which would mean that each node (set up in a RAID-1 configuration) would be able to store 375 GB of data, which is acceptable. </p>
  
  <p>My question is this if 16GB RAM is enough to efficiently serve 375 GB of data per node. The data in the application developed will also be fairly time-dependant, such that recent data will be the data most read from the database. In fact, most of the data will be deleted after about 6 months. </p>
  
  <p>Also, would I assign Cassandra a Heap (-Xmx) close to 16 GB, or does Cassandra utilize off-heap memory ? </p>