Openfire with Hazelcast Plugin & HAProxy Connection Limit

I have 3 openfire servers (version 3.9.1) on which hazelcast (Hazelcast Version 3.1.5 Build 20140115) installed. I have another server HaProxy installed

( HA-Proxy version 1.5-dev25-a339395 2014/05/10 ). I test my system using tsung installed on another machine.

Im trying to test limits of the clustered system. I have already increased open file limits of every server i mentioned.

In a single openfire server i hit more than 20k users without any problems but with the new clustered system i couldnot get more than 15k users (5k users on each openfire server) connected.

I couldnot determine the source of this problem. HaProxy or Hazelcast.

Any help would be great. Thanks…