Todd Lipcon created HDFS-3796:
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             Summary: Speed up edit log tests by avoiding fsync()
                 Key: HDFS-3796
                 URL: https://issues.apache.org/jira/browse/HDFS-3796
             Project: Hadoop HDFS
          Issue Type: Improvement
          Components: test
    Affects Versions: 3.0.0, 2.2.0-alpha
            Reporter: Todd Lipcon
            Assignee: Todd Lipcon
            Priority: Minor


Our edit log tests are very slow because they incur a lot of fsyncs as they 
write out transactions. Since fsync() has no effect except in the case of power 
outages or system crashes, and we don't care about power outages in the context 
of tests, we can safely skip the fsync without any loss in coverage.

In my tests, this sped up TestEditLog by about 5x. The testFuzzSequences test 
case improved from ~83 seconds with fsync to about 5 seconds without. These 
results are from my SSD laptop - they are probably even more drastic on 
spinning media.

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