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From "Daryn Sharp (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-4489) Use InodeID as as an identifier of a file in HDFS protocols and APIs
Date Fri, 26 Apr 2013 14:26:18 GMT

    [ https://issues.apache.org/jira/browse/HDFS-4489?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13642887#comment-13642887
] 

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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