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https://issues.apache.org/jira/browse/HDFS-4489?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13615755#comment-13615755
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Suresh Srinivas commented on HDFS-4489:
---------------------------------------
Ran some quick tests for object sizes, using
https://github.com/dweiss/java-sizeof (pretty neat stuff!)
{code}
public static void main(String[] args) {
System.out.println(RamUsageEstimator.sizeOf(new Object()));
System.out.println(RamUsageEstimator.sizeOf(new Object[0]));
System.out.println(RamUsageEstimator.sizeOf(new Object[1000000]));
}
{code}
With compressed oops on I get:
16
16
4000016
After turning it off:
16
24
8000024
> 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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