HBase: region-regionserver assignment not even

Question

I have just upgraded our hadoop cluster to Hadoop 2.2 + HBase 0.98. We have found some issues, the most critical one is that the regions are not evenly assigned over regionservers.

For example, I have one table which has 125 regions and it is assigned as following:

• hslave1 13
• hslave2 10
• hslave3 6
• hslave4 23
• hslave5 8
• hslave6 26
• hslave7 8
• hslave8 34

When we used the older version (0.94.7), we didn't have the same issue. What should be the parameters of configuration we need to check? Compaction? Split?

Thanks

Answer 1

There is a parameter in hbase-site.xml:

<property> <name>hbase.master.loadbalance.bytable</name> <value>true</value> </property>

By default, it's false. So the balance between region servers is good, but load balance at the table level is not taken into account. Set this value to true, HBase will balance the region over region servers at the table level.