User's mail: My Chamilo LMS is slow

Sir, I am a user of Chamilo 1.8 as my Website is : www.team**.in and i am having about 1300 users registered on that portal but i always face big problem with chamilo 1.8 that when i take test of all users on same day then it stops working. chamilo 1.8 is not able to handle online users more than 40, so i am facing big problem right now. Sir, i want to ask u that should i upgrade or use chamilo 2.1 so that i can handle up to 2000 users online at same time for better output. or please give me the solution for my problem . Waiting for your response! Regards M.K.
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