[jira] [Resolved] (HDFS-5046) Hang when add/remove a datanode into/from a 2 datanode cluster

["Harsh J (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HDFS-5046?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Harsh J resolved HDFS-5046.
---------------------------

    Resolution: Not A Problem

bq. a). decommission progress hangs and the status always be 'Waiting DataNode status: Decommissioned'. But, if I execute 'hadoop dfs -setrep -R 2 /', the decommission continues and will be completed finally.

The step (a) points to your problem and solution both. You have files
being created with repl=3 on a 2 DN cluster which will prevent
decommission. This is not a bug.
                
> Hang when add/remove a datanode into/from a 2 datanode cluster
> --------------------------------------------------------------
>
>                 Key: HDFS-5046
>                 URL: https://issues.apache.org/jira/browse/HDFS-5046
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: datanode
>    Affects Versions: 1.1.1
>         Environment: Red Hat Enterprise Linux Server release 5.3, 64 bit
>            Reporter: sam liu
>
> 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:
> a). decommission progress hangs and the status always be 'Waiting DataNode status: Decommissioned'. But, if I execute 'hadoop dfs -setrep -R 2 /', the decommission continues and will be completed finally.
> b). However, if the initial cluster includes >= 3 datanodes, this issue won't be encountered when add/remove another datanode. For example, if I setup a cluster with 3 datanodes, and then I can successfully add the 4th datanode into it, and then also can successfully remove the 4th datanode from the cluster.

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