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https://issues.apache.org/jira/browse/HDFS-17052?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17738000#comment-17738000
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ASF GitHub Bot commented on HDFS-17052:
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zhtttylz commented on PR #5759:
URL: https://github.com/apache/hadoop/pull/5759#issuecomment-1610928161
> > Thanks to involve me here. Skim the PR (seem very common logic), I am
wonder if this issue is only related with EC feature? or will it also impact on
replication scenario?
>
> @Hexiaoqiao The problem solved by this PR is only related to
`BlockPlacementPolicyRackFaultTolerant`.
`BlockPlacementPolicyRackFaultTolerant` has implemented a placement policy that
ensures each replica to be placed on a different rack. By default, EC files use
this policy. Replicated files can also use it if really desired.
@zhangshuyan0 's explanation is excellent,I have benefited immensely, and I
would like to provide a brief supplement.
`BlockPlacementPolicyRackFaultTolerant` enables the distribution of blocks
across multiple racks. It is the default configuration for the
`dfs.block.placement.ec.classname` Erasure Coding block placement policy.
Additionally, we can also be enabled for BlockPlacementPolicyRackFaultTolerant
by configuring `dfs.block.replicator.classname` to enable the
BlockPlacementPolicyRackFaultTolerant for replicas.
> Erasure coding reconstruction failed when num of storageType rack NOT enough
> ----------------------------------------------------------------------------
>
> Key: HDFS-17052
> URL: https://issues.apache.org/jira/browse/HDFS-17052
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: ec
> Affects Versions: 3.4.0
> Reporter: Hualong Zhang
> Assignee: Hualong Zhang
> Priority: Major
> Labels: pull-request-available
> Attachments: failed reconstruction ec in same rack-1.png, write ec in
> same rack.png
>
>
> When writing EC data, if the number of racks matching the storageType is
> insufficient, more than one block are allowed to be written to the same rack
> !write ec in same rack.png|width=962,height=604!
>
>
>
> However, during EC block recovery, it is not possible to recover on the same
> rack, which deviates from the expected behavior.
> !failed reconstruction ec in same rack-1.png|width=946,height=413!
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