Hadoop lesson learnt: Restart datanodes after modifying dfs.balance.bandwidthPerSec

I was rebalancing one of the Hadoop clusters I run at work. It was not running very fast, so I modified the appropriate setting:

  <!-- 100Mbit/s -->

I restarted the namenode and thought that would make the trick. But no, you also need to restart all your datanodes for the setting to take effect. Now I can see some action on my network graphs :-).

Written on September 10, 2010