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https://issues.apache.org/jira/browse/HDFS-5788?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13880068#comment-13880068
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Kihwal Lee commented on HDFS-5788:
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The location counting can be off if blocks are under-replicated or 
over-replicated, but spending more cycles to make it perfect will be a waste. 
So I am okay with this approach.

+1

> listLocatedStatus response can be very large
> --------------------------------------------
>
>                 Key: HDFS-5788
>                 URL: https://issues.apache.org/jira/browse/HDFS-5788
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: namenode
>    Affects Versions: 3.0.0, 0.23.10, 2.2.0
>            Reporter: Nathan Roberts
>            Assignee: Nathan Roberts
>         Attachments: HDFS-5788.patch
>
>
> Currently we limit the size of listStatus requests to a default of 1000 
> entries. This works fine except in the case of listLocatedStatus where the 
> location information can be quite large. As an example, a directory with 7000 
> entries, 4 blocks each, 3 way replication - a listLocatedStatus response is 
> over 1MB. This can chew up very large amounts of memory in the NN if lots of 
> clients try to do this simultaneously.
> Seems like it would be better if we also considered the amount of location 
> information being returned when deciding how many files to return.
> Patch will follow shortly.



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