[WorldMaker]

You can do "big data" entirely in .NET.

You can use Hadoop "Streaming" with .NET easily enough and still take advantage of the "Hadoop ecosystem".

Orleans is not exactly Hadoop, but it's close enough that conversions between are relatively straight-forward, and Orleans is useful for a number of other work distribution patterns beyond map/reduce.

Beyond that, the map/reduce pattern is one of the easiest abstractions to reimplement yourself from scratch if you get the itch. I believe Hadoop is relatively over-rated from that standpoint, and arguably IMO another case of Java developers over-ceremonializing what should be a simple, lovely abstraction/design pattern into a weird spaghetti mess of configuration and ritual.