I was refering to the documentation at: http://www.cloudera.com/documentation/enterprise/latest/topics/admin_nn_memory_config.html   But, it says that the replication factor does not impact heap size on the namenode, which does not seem correct as the data structure uses about 16 bytes for each replica. The class BlockInfo has a Datanode Descriptor that maps the nodes on which the replica's of the block are present. or to be more precise block_files of a block.   So, if I have 1 million files, with each file having 2 blocks per file, the calculations will be approximately as below:   Memory Requirements:   1 million files = 150 bytes x 1 million = 143.0511474609375 MB 6 millions blocks( replication 3) = (150 bytes per block + 16 bytes per replica = 150 bytes + 2 x16 = 182 bytes)x 6 million = 1041.412353515625 MB   Total = 1.15670259132385 GB   Am i correct or I am missing something ?   ... View more