title: data block size in HDFS, why 64MB?
body: <p>The default data block size of HDFS/Hadoop is 64MB. The block size in the disk is generally 4KB.</p>
  <p>What does 64MB block size mean? -&gt;Does it mean that the smallest unit of reading from disk is 64MB?</p>
  <p>If yes, what is the advantage of doing that?-&gt; easy for continuous access of large files in HDFS?</p>
  <p>Can we do the same by using the disk's original 4KB block size?</p>