MR3 is a new execution engine for Hadoop. Similar in spirit to Tez, it is a new execution engine with simpler design, better performance, and more features. MR3 is ready for production use as it supports all major features such as Kerberos-based security, authentication and authorization, fault-tolerance, and recovery. MR3 is implemented in Scala.
MR3 serves as a framework for running jobs in Hadoop and can work with different runtime environments. Currently its supports the runtime environment of Tez 0.9.1. MR3 also has its own runtime, called ASM, which is under development as a research project.