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Todd Lipcon commented on HDFS-4489: ----------------------------------- bq. If you have an authoritative source, please send me that Sure, from the JDK7 source code hotspot/src/share/vm/oops/arrayOop.hpp: {code} // The layout of array Oops is: // // markOop // klassOop // 32 bits if compressed but declared 64 in LP64. // length // shares klass memory or allocated after declared fields. {code} Important to note that the length of arrays is 32-bit, since array.length is an int rather than a long. So given a 64-bit field for klassId, it can use 32-bits for the actual class and 32 bits for the array length. bq. I would like to run an experiment on a large production image. But I do not have ready access to it and will have to spend time getting to it. Do you have any? Yes, I can run the experiment on a large image. Is HDFS-4434's patch ready to apply so I can test it? > 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