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Date: Fri, 1 Feb 2013 00:47:12 +0000 (UTC)
From: "Colin Patrick McCabe (JIRA)" <jira@apache.org>
To: hdfs-dev@hadoop.apache.org
Message-ID: <JIRA.12630261.1359679603206.226669.1359679632676@arcas>
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Subject: [jira] [Created] (HDFS-4461) DirectoryScanner: volume path prefix
 takes up memory for every block that is scanned
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Colin Patrick McCabe created HDFS-4461:
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             Summary: DirectoryScanner: volume path prefix takes up memory for every block that is scanned 
                 Key: HDFS-4461
                 URL: https://issues.apache.org/jira/browse/HDFS-4461
             Project: Hadoop HDFS
          Issue Type: Improvement
    Affects Versions: 2.0.3-alpha
            Reporter: Colin Patrick McCabe
            Assignee: Colin Patrick McCabe
            Priority: Minor
         Attachments: 002.patch

In the {{DirectoryScanner}}, we create a class {{ScanInfo}} for every block.  This object contains two File objects-- one for the metadata file, and one for the block file.  Since those File objects contain full paths, users who pick a lengthly path for their volume roots will end up using an extra N_blocks * path_prefix bytes per block scanned.  We also don't really need to store File objects-- storing strings and then creating File objects as needed would be cheaper.  This has been causing out-of-memory conditions for users who pick such long volume paths.

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