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https://issues.apache.org/jira/browse/HDFS-2006?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13040092#comment-13040092
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Aaron T. Myers commented on HDFS-2006:
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One option to not waste memory resources for files/directories which do not
have extended attributes set on them would be to go the same route as the
{{INodeDirectory}} vs. {{INodeDirectoryWithQuota}} classes, i.e. have
{{INodeFile}} and {{InodeFileWithXAttrs}}. Of course, this strategy requires
that we implement classes for the matrix of all the different possible
combinations of extra metadata types.
A reasonable question to ask is whether we should concern ourselves all that
much with the memory consumption of this, since the extended attributes will
presumably be per-file. Since the NN's memory is dedicated to relatively few
files and relatively many blocks, it may not matter much if we go with a fairly
naive approach.
Dhruba, do you have any data as to what percentage of the NN heap in a typical
cluster goes to per-file metadata versus per-block metadata?
> ability to support storing extended attributes per file
> -------------------------------------------------------
>
> Key: HDFS-2006
> URL: https://issues.apache.org/jira/browse/HDFS-2006
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: name-node
> Reporter: dhruba borthakur
> Assignee: dhruba borthakur
>
> It would be nice if HDFS provides a feature to store extended attributes for
> files, similar to the one described here:
> http://en.wikipedia.org/wiki/Extended_file_attributes.
> The challenge is that it has to be done in such a way that a site not using
> this feature does not waste precious memory resources in the namenode.
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