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From "Allen Wittenauer (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-1271) Decommissioning nodes not persisted between NameNode restarts
Date Tue, 29 Jun 2010 20:59:51 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1271?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12883700#action_12883700
] 

Allen Wittenauer commented on HDFS-1271:
----------------------------------------

+1.  I've just been too lazy to file a bug. :) 

> Decommissioning nodes not persisted between NameNode restarts
> -------------------------------------------------------------
>
>                 Key: HDFS-1271
>                 URL: https://issues.apache.org/jira/browse/HDFS-1271
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: name-node
>            Reporter: Travis Crawford
>
> Datanodes in the process of being decomissioned should still be decomissioning after
namenode restarts. Currently they are marked as dead after a restart.
> Details:
> Nodes can be safely removed from a cluster by marking them as decomissioned and waiting
for their data to be replicated elsewhere. This is accomplished by adding a node to the filed
referenced by dfs.hosts.excluded, then refreshing nodes.
> Decomissioning means block reports from the decomissioned datanode are no longer accepted
by the namenode, meaning for decomissioning to occur the NN must have an existing block report.
That is, a datanode can transition from: live --> decomissioning --> dead. Nodes can
NOT transition from: dead --> decomissioning --> dead.
> Operationally this is problematic because intervention is required should the NN restart
while nodes are decomissioning, meaning in-house administration tools must be more complex,
or more likely admins have to babysit the decomissioning process.
> Someone more familiar with the code might have a better idea, but perhaps the first block
report for dfs.hosts.excluded hosts should be accepted?

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