title: What is the purpose of Cassandra's commit log?
body: <p>Please some one clarify for me to understand Commit Log and its use.</p>
  
  <p>In Cassandra, while writing to Disk is the commit log the first entry point or MemTables.</p>
  
  <p>If Memtables is what is getting flushed to disk, what is the use of Commit log, is the only purpose of commit log is to server sync issues if a data node is down?</p>