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From "Walter Su (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-9918) Erasure Coding: Sort located striped blocks based on decommissioned states
Date Wed, 30 Mar 2016 01:49:25 GMT

    [ https://issues.apache.org/jira/browse/HDFS-9918?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15217217#comment-15217217

Walter Su commented on HDFS-9918:

bq. 1. Index in the logical block group. 2.Decomm status 3.Distance to the targethost
Good summary. And, If the sorting priority is 2,1, we can reuse {{DecomStaleComparator}}.

      // Move decommissioned/stale datanodes to the bottom
      Arrays.sort(di, comparator);
Because according to the javadoc of {{Arays.sort(..)}} ,
This sort is guaranteed to be stable: equal elements will not be reordered as a result of
the sort.
Also we can write a new comparator. But I think client side can handle the randomized ordering
if there's no duplication?

> Erasure Coding: Sort located striped blocks based on decommissioned states
> --------------------------------------------------------------------------
>                 Key: HDFS-9918
>                 URL: https://issues.apache.org/jira/browse/HDFS-9918
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>            Reporter: Rakesh R
>            Assignee: Rakesh R
>         Attachments: HDFS-9918-001.patch, HDFS-9918-002.patch, HDFS-9918-003.patch, HDFS-9918-004.patch,
HDFS-9918-005.patch, HDFS-9918-006.patch, HDFS-9918-007.patch
> This jira is a follow-on work of HDFS-8786, where we do decommissioning of datanodes
having striped blocks.
> Now, after decommissioning it requires to change the ordering of the storage list so
that the decommissioned datanodes should only be last node in list.
> For example, assume we have a block group with storage list:-
> d0, d1, d2, d3, d4, d5, d6, d7, d8, d9
> mapping to indices
> 0, 1, 2, 3, 4, 5, 6, 7, 8, 2
> Here the internal block b2 is duplicated, locating in d2 and d9. If d2 is a decommissioning
node then should switch d2 and d9 in the storage list.
> Thanks [~jingzhao] for the [discussions|https://issues.apache.org/jira/browse/HDFS-8786?focusedCommentId=15180415&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-15180415]

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