Networking performance

Hi I would like to ask your professional experience about switch throughput I have Gig Switchs eg: H P3400 /3500, cisco c4 948../ dlink In their spec, they said that it can handles Gig So far, I couldn't see their ports are used up over 200M in mrtg graph when I try to transfer 3G size files to files between computers ls there any limitation in those switchs? or I have to do configuration eg: put it full duplex instead of auto Thank you for your help