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From "Lu Yilei (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-1435) Provide an option to store fsimage compressed
Date Thu, 14 Oct 2010 11:43:36 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1435?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12920929#action_12920929
] 

Lu Yilei commented on HDFS-1435:
--------------------------------

to Kuang,  If the fsimage is very big. The network is full in a short time when SeconaryNamenode
do checkpoint, leading to Jobtracker access Namenode to get relevant file data to fail in
job initialization phase. So we limit transmission speed and compress transmission to resolve
the problem. 
We have complete the development and testing. But we not add the code that check NameNode
fsimage and SecondaryNameNode when download CheckpointFiles. Because it may lead to other
risks.
Please see the patch that limit transmission speed and compress transmission.
Next I will contribute other patch that check NameNode fsimage and SecondaryNameNode when
download CheckpointFiles. Thanks.

> Provide an option to store fsimage compressed
> ---------------------------------------------
>
>                 Key: HDFS-1435
>                 URL: https://issues.apache.org/jira/browse/HDFS-1435
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: name-node
>    Affects Versions: 0.22.0
>            Reporter: Hairong Kuang
>            Assignee: Hairong Kuang
>             Fix For: 0.22.0
>
>         Attachments: trunkImageCompress.patch, trunkImageCompress1.patch
>
>
> Our HDFS has fsimage as big as 20G bytes. It consumes a lot of network bandwidth when
secondary NN uploads a new fsimage to primary NN.
> If we could store fsimage compressed, the problem could be greatly alleviated.
> I plan to provide a new configuration hdfs.image.compressed with a default value of false.
If it is set to be true, fsimage is stored as compressed.
> The fsimage will have a new layout with a new field "compressed" in its header, indicating
if the namespace is stored compressed or not.

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