MongoDB: What's the point of using MapReduce without parallelism?

Question

Quoting http://www.mongodb.org/display/DOCS/MapReduce#MapReduce-Parallelism

As of right now, MapReduce jobs on a single mongod process are single thre

Answer 1

M/R is already parallel in MongoDB if you're running a sharded cluster. This is the main point of M/R anyway - to put the computation on the same node as the data.