I am trying to tune my vSphere 5 and virtualized SAN for performance, but the network adapters for all networks seems to be stuck at 100Mb Full duplex instead of 1000Mb Full duplex. Does this mean that all communications between VM's on the all virtual networks is stuck at 100Mb full duplex, even though many VM's use the vmxnet3 drivers? How can I fix this?
Communications between virtual machines on the same vSwitch on the same box will be very fast and will not traverse the physical uplinks unless they are assigned to separate port groups that use an upstream device for inter-vlan routing. If your physical links are showing 100Mb, then your issue is probably the physical switch those NICs are connected to.