YARN is now an Apache sub-project for Hadoop along with HDFS and MapReduce.
Hadoop YARN is a MapReduce upgrade that takes Apache Hadoop beyond MapReduce for data-processing.
Apache Hadoop YARN joins Hadoop Common (core libraries), Hadoop HDFS (storage) and Hadoop MapReduce (the MapReduce implementation) as the sub-projects of the Apache Hadoop which, itself, is a Top Level Project in the Apache Software Foundation.
Arun Murthy (Hortonworks Cofounder) announces the new project in a blog post. Here is his announcement:
As folks are aware, Hadoop HDFS is the data storage layer for Hadoop and MapReduce was the data-processing layer. However, the MapReduce algorithm, by itself, isn’t sufficient for the very wide variety of use-cases we see Hadoop being employed to solve. With YARN, Hadoop now has a generic resource-management and distributed application framework, where by, one can implement multiple data processing applications customized for the task at hand. Hadoop MapReduce is now one such application for YARN and I see several others given my vantage point – in future you will see MPI, graph-processing, simple services etc.; all co-existing with MapReduce applications in a Hadoop YARN cluster.