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https://issues.apache.org/jira/browse/HDFS-1476?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12933512#action_12933512
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Hairong Kuang commented on HDFS-1476:
-------------------------------------

I really like this idea. It is simple, does not need lot of code change, but 
should work out very well. It has an extra bonus to make exiting safemode 
quicker.

On minor comment, the default value of the threshold is better to be the 
safemode exiting threshold.

> listCorruptFileBlocks should be functional while the name node is still in 
> safe mode
> ------------------------------------------------------------------------------------
>
>                 Key: HDFS-1476
>                 URL: https://issues.apache.org/jira/browse/HDFS-1476
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>            Reporter: Patrick Kling
>            Assignee: Patrick Kling
>         Attachments: HDFS-1476.2.patch, HDFS-1476.patch
>
>
> This would allow us to detect whether missing blocks can be fixed using Raid 
> and if that is the case exit safe mode earlier.
> One way to make listCorruptFileBlocks available before the name node has 
> exited from safe mode would be to perform a scan of the blocks map on each 
> call to listCorruptFileBlocks to determine if there are any blocks with no 
> replicas. This scan could be parallelized by dividing the space of block IDs 
> into multiple intervals than can be scanned independently.

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