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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-1071) savenamespace should write the fsimage to all configured fs.name.dir in parallel
Date Thu, 21 Oct 2010 00:45:24 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1071?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12923265#action_12923265
] 

dhruba borthakur commented on HDFS-1071:
----------------------------------------

I think the FSnamesystem lock ensures that the same image is being written to all the directories.
how is it possible that the images could be different? The saveFSImage acquires the writeLock
and then writes all the copies in parallel, isn't it?

> savenamespace should write the fsimage to all configured fs.name.dir in parallel
> --------------------------------------------------------------------------------
>
>                 Key: HDFS-1071
>                 URL: https://issues.apache.org/jira/browse/HDFS-1071
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: name-node
>            Reporter: dhruba borthakur
>            Assignee: Dmytro Molkov
>         Attachments: HDFS-1071.2.patch, HDFS-1071.3.patch, HDFS-1071.4.patch, HDFS-1071.5.patch,
HDFS-1071.6.patch, HDFS-1071.patch
>
>
> If you have a large number of files in HDFS, the fsimage file is very big. When the namenode
restarts, it writes a copy of the fsimage to all directories configured in fs.name.dir. This
takes a long time, especially if there are many directories in fs.name.dir. Make the NN write
the fsimage to all these directories in parallel.

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