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https://issues.apache.org/jira/browse/HDFS-9657?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15152003#comment-15152003
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Li Bo commented on HDFS-9657:
-----------------------------

Thanks Zhe’s comment.

90% errors are transient and without permanent data loss, postponing the 
recoveries may reduce a lot of unnecessary work. Configuring the task number by 
time segments is a solution. I have just created HDFS-9826 which delays the 
recoveries for a configured time period. I am thinking about how to combine 
them together.


> Schedule EC tasks at proper time to reduce the impact of recovery traffic
> -------------------------------------------------------------------------
>
>                 Key: HDFS-9657
>                 URL: https://issues.apache.org/jira/browse/HDFS-9657
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>            Reporter: Li Bo
>            Assignee: Li Bo
>         Attachments: HDFS-9657-001.patch, HDFS-9657-002.patch
>
>
> The EC recover tasks consume a lot of network bandwidth and disk I/O. 
> Recovering a corrupt block requires transferring 6 blocks , hence creating a 
> 6X overhead in network bandwidth and disk I/O.  When a datanode fails , the 
> recovery of the whole blocks on this datanode may use up the network 
> bandwith.  We need to start a recovery task at a proper time in order to give 
> less impact to the system.



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