[luv-beginners] what is happening

hi I have 2 boxes side by side both have gigabit ethernet connected to a switch on the desk. The source is an i3-550 with /home mounted from an md0-array of 4*1TB drives in a raid5 config and the sink is an E2200 with /home on 1 disk and an nfs mount point issue command mv Fedora-18-x64.iso from source sink. The transfer starts at 350Mb/s for about 200MB then drops to 500kb/s for the rest. Steve