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From "Hairong Kuang (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HDFS-1435) Provide an option to store fsimage compressed
Date Mon, 11 Oct 2010 21:59:35 GMT

     [ https://issues.apache.org/jira/browse/HDFS-1435?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Hairong Kuang updated HDFS-1435:
--------------------------------

    Attachment: trunkImageCompress.patch

This patch changed the fsimage's format to support compression. The third field in the header
(isCompressed) indicates if the image is stored as compressed. If yes, the fourth field stores
the compression codec.

The HDFS admin could configure if s/he wants to store fsimage compressed and which codec is
used to compress its fsimage. The codec to be used for storing or reading an fsimage has to
be one of the codecs specified in io.compression.codecs or be either GzipCodec or DefaultCodec
if io.compression.codecs is not configured. 

> 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
>
>
> 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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