Hi, I am really interested in learning Hadoop and Mapreduce. I know Java pretty well. what more do i need to know well before i can start on Hadoop? Also can you please direct me to genuine online resources where i can learn this?
If you are already an experienced Java developer then the next step is to grab a download and start playing with Hadoop. You can get either the software from one of the distribution homepages or even a pre-configured VM with everything configured from Cloudera at least, possibly Horton works too.
If you want to understand more of the underlying theory read the original Google papers on MapReduce and the Google File System (GFS) they are quite accessible for academic papers and have become absolute classics.