Hadoop YARN is the architectural center of Hadoop that allows multiple data processing engines such as interactive SQL, real-time streaming, data science and batch processing to handle data stored on a single platform, unlocking an entirely new approach to analytics. YARN is the foundation of the new generation of Hadoop and is enabling organizations everywhere to realize a modern data architecture. YARN also extends the power of Hadoop to incumbent and new technologies found within the data center so that they can take advantage of cost effective, linear-scale storage and processing. It provides ISVs and developers a consistent framework for writing data access applications that run IN Hadoop. As its architectural center, YARN enhances a Hadoop compute cluster in the following ways: Multitenancy, Cluster utilization, Scalability and Compatibility. Multi-tenant data processing improves an enterprises’ return on Hadoop investments. YARNs dynamic allocation of cluster resources improves utilization over more static MapReduce rules. YARN’s resource manager focuses exclusively on scheduling and keeps pace as clusters expand to thousands of nodes. Existing MapReduce applications developed for Hadoop 1 can run YARN without any disruptions to the processes that already work.
If you need more detailed knowledge on YARN, I would recommend one of these books: