Next Generation MapReduce Architecture.
'Next Generation MR' or 'NextGen MR' or 'MRv2' or 'MR2' is a major revamp of the MapReduce engine and will part of the 0.23 release. MRv1 or the old MapReduce engine will be not be supported in 0.23 release. The underlying engine has been revamped in 0.23, but the API to interface with the engine remains the same. So, the existing MapReduce code for MRv1 engine should run without modifications on MRv2.
