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https://issues.apache.org/jira/browse/HDFS-11634?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15963055#comment-15963055
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Rushabh S Shah commented on HDFS-11634:
---------------------------------------

Overall the patch looks good.
But I have one question.
In the patch , should the line {{if(numBlocks < s) {}} be {{if(numBlocks '<=' 
s) {}} ?
{noformat}
  if(numBlocks < s) {
         index++;
         s -= numBlocks;
       }
{noformat}


> Optimize BlockIterator when interating starts in the middle.
> ------------------------------------------------------------
>
>                 Key: HDFS-11634
>                 URL: https://issues.apache.org/jira/browse/HDFS-11634
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>    Affects Versions: 2.6.5
>            Reporter: Konstantin Shvachko
>            Assignee: Konstantin Shvachko
>         Attachments: HDFS-11634.001.patch
>
>
> {{BlockManager.getBlocksWithLocations()}} needs to iterate blocks from a 
> randomly selected {{startBlock}} index. It creates an iterator which points 
> to the first block and then skips all blocks until {{startBlock}}. It is 
> inefficient when DN has multiple storages. Instead of skipping blocks one by 
> one we can skip entire storages. Should be more efficient on average.



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