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:
<property> <!-- 100Mbit/s --> <name>dfs.balance.bandwidthPerSec</name> <value>104857600</value> </property>
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 :-).