title: Measure throughput at datanode
body: <p>I want to measure the throughput at each datanode by measuring the time taken for each read/write operation. It is very confusing to read through the million functions and find out where this is happening. Could someone list the series of calls made while reading/writing a block of data?  am using version 1.0.1. Alternatively, if there is already an API which measures this at the datanode I could use that information.</p>