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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). -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators For more information on JIRA, see: http://www.atlassian.com/software/jira