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https://issues.apache.org/jira/browse/HDFS-13157?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17168982#comment-17168982
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Hadoop QA commented on HDFS-13157:
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| (x) *{color:red}-1 overall{color}* |
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|| Vote || Subsystem || Runtime || Comment ||
| {color:blue}0{color} | {color:blue} reexec {color} | {color:blue}  0m  
0s{color} | {color:blue} Docker mode activated. {color} |
| {color:red}-1{color} | {color:red} patch {color} | {color:red}  0m  5s{color} 
| {color:red} https://github.com/apache/hadoop/pull/1391 does not apply to 
trunk. Rebase required? Wrong Branch? See 
https://wiki.apache.org/hadoop/HowToContribute for help. {color} |
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|| Subsystem || Report/Notes ||
| GITHUB PR | https://github.com/apache/hadoop/pull/1391 |
| JIRA Issue | HDFS-13157 |
| Console output | 
https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-1391/3/console |
| versions | git=2.17.1 |
| Powered by | Apache Yetus 0.12.0 https://yetus.apache.org |


This message was automatically generated.



> Do Not Remove Blocks Sequentially During Decommission 
> ------------------------------------------------------
>
>                 Key: HDFS-13157
>                 URL: https://issues.apache.org/jira/browse/HDFS-13157
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: datanode, namenode
>    Affects Versions: 3.0.0
>            Reporter: David Mollitor
>            Assignee: David Mollitor
>            Priority: Major
>         Attachments: HDFS-13157.1.patch
>
>
> From what I understand of [DataNode 
> decommissioning|https://github.com/apache/hadoop/blob/42a1c98597e6dba2e371510a6b2b6b1fb94e4090/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/DatanodeAdminManager.java]
>  it appears that all the blocks are scheduled for removal _in order._. I'm 
> not 100% sure what the ordering is exactly, but I think it loops through each 
> data volume and schedules each block to be replicated elsewhere. The net 
> affect is that during a decommission, all of the DataNode transfer threads 
> slam on a single volume until it is cleaned out. At which point, they all 
> slam on the next volume, etc.
> Please randomize the block list so that there is a more even distribution 
> across all volumes when decommissioning a node.



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