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https://issues.apache.org/jira/browse/HDFS-12119?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16923634#comment-16923634
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Kihwal Lee commented on HDFS-12119:
-----------------------------------
Is it same as HDFS-3457?
> Inconsistent "Number of Under-Replicated Blocks" shown on HDFS web UI and
> fsck report
> --------------------------------------------------------------------------------------
>
> Key: HDFS-12119
> URL: https://issues.apache.org/jira/browse/HDFS-12119
> Project: Hadoop HDFS
> Issue Type: Bug
> Affects Versions: 2.6.0
> Reporter: liuyiyang
> Priority: Major
> Attachments: HDFS-12119.001.patch
>
>
> Sometimes the information "Number of Under-Replicated Blocks" shown on
> NameNode web UI is inconsistent with the "Under-replicated blocks"
> information shown in fsck report.
> It's easy to reproduce such a case as follows:
> 1、In a cluster with DN1(rack0)、DN2(rack1) and DN3(rack2) which stores a lot
> of blocks, the replication factor is set to 2;
> 2、Re-allocate racks as DN1(rack0)、DN2(rack1) and DN3(rack1) ;
> 3、Restart HDFS daemons.
> Then you can find inconsistent "Number of Under-Replicated Blocks" on web ui
> and "Under-replicated blocks" in fsck result.
> I dug into the source code and found that "Number of Under-Replicated
> Blocks" on web ui consists of blocks that have less than target number of
> replicas and blocks that have the right number of replicas, but which the
> block manager felt were badly distributed. In fsck result, "Under-replicated
> blocks" are the blocks that have less than target number of replicas, and
> "Mis-replicated blocks" are the blocks that are badly distributed. So the
> Under-Replicated Blocks info on web UI and fsck result may be inconsistent.
> Since Under-Replicated Blocks means higer missing risk for blocks, when
> threre is no blocks that have less than target replicas but a lot of blocks
> that have the right number of blocks but are badlly distributed, the "Number
> of Under-Replicated Blocks" on web UI will be same as number of
> "Mis-replicated blocks", which is misleading for users.
> It would be clear to make "Number of Under-Replicated Blocks" on web UI be
> consistent with "Under-replicated blocks" in fsck result.
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