Been testing the speed of my drives over my home network using LanSpeed.
Usually I get about 170 Mbps read, which I like - gigabit network. However, sometimes I get around 550 Mbps!! I can't effectively reproduce it, but it seems to be something to do with when I map the drive. When I get that speed, I can rerun the tests for a while and get the same sort of speed, and then it will go back to around 170.
I have two computers on the network - brand new quad core i7 desktop and dual core laptop. WNDR4000 router in between. Gigabit throughout. These numbers are for both hardwired into router, and running LanSpeed from laptop to desktop hard drive.
It's more than likely miscalcuatling the speed due to caching or something. 170Mbps is slow for a Gbit network (if thats 170MB/sec that's faster than Gbit can theoretically achieve). 550Mbps is closer to the real-world maximum for Gbit with jumbo frames and is drastically affected by latency.