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From "Jing Zhao (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-1172) Blocks in newly completed files are considered under-replicated too quickly
Date Mon, 05 Oct 2015 21:43:27 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1172?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14944105#comment-14944105
] 

Jing Zhao commented on HDFS-1172:
---------------------------------

bq. I'm trying to update the pendingReplications only in the code path of completeFile now

Yeah, good idea. We can do it not necessarily in checkReplication, but in file completion
stage.

> Blocks in newly completed files are considered under-replicated too quickly
> ---------------------------------------------------------------------------
>
>                 Key: HDFS-1172
>                 URL: https://issues.apache.org/jira/browse/HDFS-1172
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: namenode
>    Affects Versions: 0.21.0
>            Reporter: Todd Lipcon
>            Assignee: Masatake Iwasaki
>         Attachments: HDFS-1172-150907.patch, HDFS-1172.008.patch, HDFS-1172.009.patch,
HDFS-1172.010.patch, HDFS-1172.patch, hdfs-1172.txt, hdfs-1172.txt, replicateBlocksFUC.patch,
replicateBlocksFUC1.patch, replicateBlocksFUC1.patch
>
>
> I've seen this for a long time, and imagine it's a known issue, but couldn't find an
existing JIRA. It often happens that we see the NN schedule replication on the last block
of files very quickly after they're completed, before the other DNs in the pipeline have a
chance to report the new block. This results in a lot of extra replication work on the cluster,
as we replicate the block and then end up with multiple excess replicas which are very quickly
deleted.



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