New Features in CDH 5
This section lists new features in CDH 5. See What's New in CDH 5 Beta 1 for more information. For links to the detailed change lists that describe the bug fixes and improvements to all of the projects, including bug-fix reports for the corresponding upstream Apache projects, see the packaging section of CDH Packaging and Tarball Information.
About Apache Hadoop MapReduce Version 1 (MRv1) and Version 2 (MRv2 or YARN)
- MapReduce 2.0 (MRv2 or YARN): CDH 5 includes MapReduce 2.0 (MRv2 or YARN). The fundamental idea of the YARN architecture is to split up the two primary responsibilities of the JobTracker — resource management and job scheduling/monitoring — into separate daemons: a global ResourceManager (RM) and per-application ApplicationMasters (AM). With MRv2, the ResourceManager (RM) and per-node NodeManagers (NM), form the data-computation framework. The ResourceManager service effectively replaces the functions of the JobTracker, and NodeManagers run on slave nodes instead of TaskTracker daemons. The per-application ApplicationMaster is, in effect, a framework-specific library and is tasked with negotiating resources from the ResourceManager and working with the NodeManager(s) to execute and monitor the tasks. For details of the new architecture, see Apache Hadoop NextGen MapReduce (YARN).
- MapReduce Version 1 (MRv1): For
backward compatibility, CDH 5 continues to support the original MapReduce framework (i.e.
the JobTracker and TaskTrackers), but you should begin migrating to MRv2. Note
Cloudera does not support running MRv1 and YARN daemons on the same nodes at the same time.
- Deprecated properties:
In Hadoop 2.0.0 and later (MRv2), a number of Hadoop and HDFS properties have been deprecated. (The change dates from Hadoop 0.23.1, on which the Beta releases of CDH 4 were based). A list of deprecated properties and their replacements can be found at Hadoop Deprecated Properties.Note
:All of these deprecated properties continue to work in MRv1. Conversely the new mapreduce* properties listed do not work in MRv1.