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From "Andrew Wang (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-4305) Add a configurable limit on number of blocks per file, and min block size
Date Fri, 22 Mar 2013 02:41:17 GMT

     [ https://issues.apache.org/jira/browse/HDFS-4305?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Andrew Wang updated HDFS-4305:
------------------------------

    Attachment: hdfs-4305-1.patch

Took a hack at this, patch attached.

I set the default to 0 for the min block size. Going non-zero I think would break a lot of
tests since they set small block sizes, and would be an incompatible change.

For the max number of blocks per file, I chose 1 million. I figure with the default 64MB block
size, that's a 64TB file.

Feedback appreciated, especially if these defaults should be altered.
                
> 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
>            Assignee: Andrew Wang
>            Priority: Minor
>         Attachments: hdfs-4305-1.patch
>
>
> 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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