[jira] [Reopened] (HDFS-97) DFS should detect slow links(nodes) and avoid them

["Harsh J (Reopened) (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HDFS-97?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Harsh J reopened HDFS-97:
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Oh well, didn't notice the 'read' issue too. We cover writes with that, not reads. Reopening.
                
> DFS should detect slow links(nodes) and avoid them
> --------------------------------------------------
>
>                 Key: HDFS-97
>                 URL: https://issues.apache.org/jira/browse/HDFS-97
>             Project: Hadoop HDFS
>          Issue Type: Bug
>            Reporter: Runping Qi
>
> The current DFS does not detect slow links (nodes).
> Thus, when a node or its network link is slow, it may affect the overall system performance significantly.
> Specifically, when a map job needs to read data from such a node, it may progress 10X slower.
> And when a DFS data node pipeline consists of such a node, the write performance degrades significantly.
> This may lead to some long tails for map/reduce jobs. We have experienced such behaviors quite often.

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