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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-4305) Add a configurable limit on number of blocks per file, and min block size
Date Thu, 13 Dec 2012 01:02:08 GMT

    [ https://issues.apache.org/jira/browse/HDFS-4305?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13530557#comment-13530557
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Todd Lipcon commented on HDFS-4305:
-----------------------------------

I believe in this case it was OP_ADD, but I'm not certain of that (I don't have a copy of
the logs unfortunately).

I agree we could probably optimize these further, but regardless, I think it makes sense to
limit users to a "reasonable" number of blocks to prevent them from shooting themselves in
the foot.
                
> Add a configurable limit on number of blocks per file, and min block size
> -------------------------------------------------------------------------
>
>                 Key: HDFS-4305
>                 URL: https://issues.apache.org/jira/browse/HDFS-4305
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: namenode
>    Affects Versions: 1.0.4, 3.0.0, 2.0.2-alpha
>            Reporter: Todd Lipcon
>            Priority: Minor
>
> We recently had an issue where a user set the block size very very low and managed to
create a single file with hundreds of thousands of blocks. This caused problems with the edit
log since the OP_ADD op was so large (HDFS-4304). I imagine it could also cause efficiency
issues in the NN. To prevent users from making such mistakes, we should:
> - introduce a configurable minimum block size, below which requests are rejected
> - introduce a configurable maximum number of blocks per file, above which requests to
add another block are rejected (with a suitably high default as to not prevent legitimate
large files)

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