There is an approximate limit of 1000 active connections  per node in OneFS Version 6.5.X.  This limit increase significantly in 7.0.X, and can be as high as 10,000 connections per node.  Idle connection counts are approximately 10,000 (6.5.X) and 50,000 (7.0.X).
What is the maximum number of client connections that Isilon can handle?
Client connections per node