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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-1547) Improve decommission mechanism
Date Fri, 07 Jan 2011 07:51:47 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1547?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12978667#action_12978667
] 

dhruba borthakur commented on HDFS-1547:
----------------------------------------

> It is not clear if the "decommisioned" state will have active heartbeats.

I agree. I am suggesting that this JIRA do not mess with heartbeats/blockreport frequencies
for decommissioned datanodes. That is mostly an optimization and I am not sue whether it is
worth the complexity, of course we can discuss it in another jira.

>  I am concerned not shutting down datanode could result in namenode using decommissioned
nodes in unintended ways. 

This is a vald concern. What if the list of datanodes returned via getBlockLocations is such
that the datanodes that are in the "decommisioned" state are always listed last? This will
decrease the probability that clients will ever use the decommissioned nodes to read data.
That should help alleviate this concern, isn't it?

Otherwise, +1 to Suresh's proposal.

> Improve decommission mechanism
> ------------------------------
>
>                 Key: HDFS-1547
>                 URL: https://issues.apache.org/jira/browse/HDFS-1547
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: name-node
>    Affects Versions: 0.23.0
>            Reporter: Suresh Srinivas
>            Assignee: Suresh Srinivas
>             Fix For: 0.23.0
>
>
> Current decommission mechanism driven using exclude file has several issues. This bug
proposes some changes in the mechanism for better manageability. See the proposal in the next
comment for more details.

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