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https://issues.apache.org/jira/browse/HDFS-4489?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13642887#comment-13642887
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Daryn Sharp commented on HDFS-4489:
-----------------------------------
I don't think Nathan and I are questioning the utility of the feature, but need
to get a feel for the possible performance impact. _If_ there is a significant
degradation then it will delay our adoption of 2.x until it's optimized.
I think a good performance test is to create a namespace of 150M paths. Flood
the NN with thousands of concurrent file & directory add/deletes per second
throughout the namespace. Hopefully there is existing benchmark with those
properties.
> Use InodeID as as an identifier of a file in HDFS protocols and APIs
> --------------------------------------------------------------------
>
> Key: HDFS-4489
> URL: https://issues.apache.org/jira/browse/HDFS-4489
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: namenode
> Reporter: Brandon Li
> Assignee: Brandon Li
> Fix For: 2.0.5-beta
>
>
> The benefit of using InodeID to uniquely identify a file can be multiple
> folds. Here are a few of them:
> 1. uniquely identify a file cross rename, related JIRAs include HDFS-4258,
> HDFS-4437.
> 2. modification checks in tools like distcp. Since a file could have been
> replaced or renamed to, the file name and size combination is no t reliable,
> but the combination of file id and size is unique.
> 3. id based protocol support (e.g., NFS)
> 4. to make the pluggable block placement policy use fileid instead of
> filename (HDFS-385).
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