This is a general switch architecture question. Let's say there are 2 workstations communicating with a server. All three nodes are using gigabit NICs and they're connected to a gigabit switch. Workstation A can send data to the server at 35MB/s when only workstation A is sending. Likewise workstation B can send data to the server at 35MB/s when only workstation B is sending. When both workstation A & workstation B send data to the server simultaneously however, the transfer rate for both drops to about 6MB/s.
The 6MB/s figure seems to me to be well below the rate that it should be. What is typical transfer rate one should expect in this scenario? Also what woud be a likely cause of such a dramatic decrease in performance like this? (Assume that the workstations and server are not to blame for the bottleneck) Would the switch buffers be to blame? If the switch is doing store-and-forward as opposed to cut-through processing, could that be a factor?