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From "Zhe Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-6898) DN must reserve space for a full block when an RBW block is created
Date Mon, 25 Aug 2014 22:50:59 GMT

    [ https://issues.apache.org/jira/browse/HDFS-6898?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14109909#comment-14109909
] 

Zhe Zhang commented on HDFS-6898:
---------------------------------

[~cmccabe] Will {{fallocate}} trigger disk I/O? I thought it only manipulates metadata: http://linux.die.net/man/1/fallocate
-- "this is done quickly by allocating blocks and marking them as uninitialized, requiring
no IO to the data blocks"

> DN must reserve space for a full block when an RBW block is created
> -------------------------------------------------------------------
>
>                 Key: HDFS-6898
>                 URL: https://issues.apache.org/jira/browse/HDFS-6898
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: datanode
>    Affects Versions: 2.5.0
>            Reporter: Gopal V
>            Assignee: Arpit Agarwal
>         Attachments: HDFS-6898.01.patch, HDFS-6898.03.patch
>
>
> DN will successfully create two RBW blocks on the same volume even if the free space
is sufficient for just one full block.
> One or both block writers may subsequently get a DiskOutOfSpace exception. This can be
avoided by allocating space up front.



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