Merge -c 1368724 from branch-1 to branch-1 to fix MAPREDUCE-3289. Make use of fadvise in the NM's shuffle handler.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1.1@1389970 13f79535-47bb-0310-9956-ffa450edef68
Merge -c 1373672 from branch-1 to branch-1 to fix MAPREDUCE-4511. Add IFile readahead.

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Merge -c 1366285 from branch-1 to branch-1.1 to fix MAPREDUCE-1906. Lower minimum heartbeat interval between tasktracker and JobTracker for smaller clusters.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1.1@1389995 13f79535-47bb-0310-9956-ffa450edef68
Merge -c 1356904 from branch-1 to branch-1.1 to fix MAPREDUCE-3837. Job tracker is not able to recover job in case of crash and after that no user can submit job.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1.1@1390006 13f79535-47bb-0310-9956-ffa450edef68
Merge -c 1374095 from branch-1 to branch-1.1 to fix MAPREDUCE-4558. Disable TestJobTrackerSafeMode.

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Merge -c 1377714 from branch-1 to branch-1.1 to fix MAPREDUCE-4328. Add a JobTracker safemode to allow it to be resilient to NameNode failures.

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Merge -c 1365591 from branch-1 to branch-1.1 to fix HADOOP-8617. Backport HADOOP-6148, HADOOP-6166 and HADOOP-7333 for a pure Java CRC32 calculator implementation.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1.1@1390022 13f79535-47bb-0310-9956-ffa450edef68
Merge -c 1365881 from branch-1 to branch-1.1 to fix HDFS-496. Backport: Use PureJavaCrc32 in HDFS.

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Merge -c 1366280 from branch-1 to branch-1.1 to fix MAPREDUCE-782. Use PureJavaCrc32 in mapreduce spills.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1.1@1390029 13f79535-47bb-0310-9956-ffa450edef68
Merge -c 1379203 from branch-1 to branch-1.1 to fix HADOOP-8748. Refactor DFSClient retry utility methods to a new class in org.apache.hadoop.io.retry.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1.1@1390031 13f79535-47bb-0310-9956-ffa450edef68
Merge -c 1368350 from branch-1 to branch-1.1 to fix HDFS-3667.  Add retry support to WebHdfsFileSystem.

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Merge -c 1379746 from branch-1 to branch-1.1 to fix HDFS-3871. Change DFSClient to use RetryUtils.

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Merge -c 1390041 from branch-1 to branch-1.1 to fix MAPREDUCE-4603. Add support for JobClient to retry job-submission when JobTracker is in SafeMode. Contributed by Arun C. Murthy.

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