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Date: Thu, 11 Apr 2013 13:45:18 +0000 (UTC)
From: "Daryn Sharp (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Message-ID: <JIRA.12631775.1360608342450.149382.1365687918883@arcas>
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Subject: [jira] [Commented] (HDFS-4489) Use InodeID as as an identifier of a
 file in HDFS protocols and APIs
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    [ https://issues.apache.org/jira/browse/HDFS-4489?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13628931#comment-13628931 ] 

Daryn Sharp commented on HDFS-4489:
-----------------------------------

bq. {quote}Perhaps ASN.1 encoding the long for the inode id will significantly decrease the memory consumption?{quote}
bq. Can you add more details on how this would decrease memory consumption?

If the long is encoded as a variable length byte array, it should take a long time to exceed 4-5 bytes.  With minimal effort & complexity, the memory increase would nominally be cut in half for many deployments.  Just a suggestion.
                
> 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
>
> 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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