-Hang when add/remove a datanode into/from a 2 datanode cluster
sam liu 2013-06-21, 09:29
I encountered an issue which hangs the decommission operatoin. Its steps:
1. Install a Hadoop 1.1.1 cluster, with 2 datanodes: dn1 and dn2. And, in
hdfs-site.xml, set the 'dfs.replication' to 2
2. Add node dn3 into the cluster as a new datanode, and did not change the '
dfs.replication' value in hdfs-site.xml and keep it as 2
note: step 2 passed
3. Decommission dn3 from the cluster
Expected result: dn3 could be decommissioned successfully
Actual result: decommission progress hangs and the status always be
'Waiting DataNode status: Decommissioned'
However, if the initial cluster includes >= 3 datanodes, this issue won't
be encountered when add/remove another datanode.
Also, after step 2, I noticed that some block's expected replicas is 3, but
the 'dfs.replication' value in hdfs-site.xml is always 2!
Could anyone pls help provide some triages?
Thanks in advance!