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Date: Thu, 31 May 2007 14:59:15 -0700 (PDT)
From: "Doug Cutting (JIRA)" <jira@apache.org>
To: hadoop-dev@lucene.apache.org
Subject: [jira] Created: (HADOOP-1450) checksums should be closer to data
 generation and consumption
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checksums should be closer to data generation and consumption
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                 Key: HADOOP-1450
                 URL: https://issues.apache.org/jira/browse/HADOOP-1450
             Project: Hadoop
          Issue Type: Improvement
          Components: fs
            Reporter: Doug Cutting
             Fix For: 0.14.0


ChecksumFileSystem checksums data by inserting a filter between two buffers.  The outermost buffer should be as small as possible, so that, when writing, checksums are computed before the data has spent much time in memory, and, when reading, checksums are validated as close to their time of use as possible.  Currently the outer buffer is the larger, using the bufferSize specified by the user, and the inner is small, so that most reads and writes will bypass it, as an optimization.  Instead, the outer buffer should be made to be bytesPerChecksum, and the inner buffer should be the user-specified buffer size.

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