Biggest cluster running YARN in the world?

[Tan, Wangda]

Hi guys,
I've a question in my head for a long time, what's the biggest cluster running 
YARN? I just heard some "rumor" about some biggest cluster running map-reduce 
1.0 with 10,000+ nodes, but rarely heard about such "rumor" about YARN.
Welcome any message about this, like "inside information" or "rumor" :-p.
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Thanks,
Wangda