title: Clarity of terms used in HDFS?
body: <p>I have come across several terms while getting familiar to HDFS. Few of the terms are like: <code>namespace</code>, <code>metadata</code>, <code>transaction logs</code>, <code>fsimage</code>, <code>editlogs</code>.</p>
  
  <p>Sometimes it appears that all these terms describe same thing, which is "having some information", but i am not clear on this.</p>
  
  <p>In general <code>metadata</code> means data about data so would <code>metadata</code> refer to all these terms or all these terms have different purpose in context of Hadoop HDFS?</p>