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https://issues.apache.org/jira/browse/HDFS-1435?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12921170#action_12921170
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Todd Lipcon commented on HDFS-1435:
-----------------------------------
Hey Hairong. Another idea which you may want to experiment with at some point
is to write a BufferedInputStream equivalent that does "readahead" or buffer
filling in a second thread. That way the extra CPU caused by compression goes
onto another core. Given that the actual application of the image data to the
namespace is single-threaded due to the FSN lock, I bet compressed reading
could actually get faster than uncompressed.
> 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: checkpoint-limitandcompress.patch,
> 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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