private void checkAndEraseData(byte[] actual, int from, byte[] expected, String message) {
    for (int idx = 0; idx < actual.length; idx++) {
      assertEquals(message + " byte " + (from + idx) + " differs. expected " + expected[from + idx]
        + " actual " + actual[idx], actual[idx], expected[from + idx]);
      actual[idx] = 0;
    }
  }
Ugly test that ensures we can get at the hedged read counters in dfsclient. Does a bit of
preading with hedged reads enabled using code taken from hdfs TestPread.
hbase-server/src/test/java/org/apache/hadoop/hbase/util/TestFSUtils.java