Solving Transfer Speed Drop Gigabit Network Windows 7/2008 Server R2
I bought a new Gigabit Switch this week, so I could use my fileserver as a fileserver…
My workstation runs Windows 7 and my Server runs currently Windows Server 2008 R2.
I happily saw a 3GB Iso file transferred with 80 Megabyte/Sec. But suddenly just before the end, the speed dropped to around 10 Megabyte/Sec. I suspected the switch in being the troublemaker, but the leds indicated that we still were on Gigabit instead of 100mbit. Running Iperf confirmed this.
So, it wasn’t the network, it was the server. Looking around the internet it turns out that most likely it was the diskspeed. That was strange, since I have a Raid5 array in the fileserver, and it surely could handle 50megabyte at least. Well, it turned out something was wrong with my write cache settings.
Somehow I had decided one day that it was a bad idea to have the write cache enabled for my raid5 array. Strange thing was that in the devicemanager it was enabled. But when I looked into the intel storage manager, it was actually disabled. Fortunately a simple option there made it enabled.
Now the transfer didn’t slow down at the end, and I now have full speed the whole time. (That is, when transferring large files, lots of small files will definitely be always slow).
Some info: The memory usage on the server grew and grew when the speed was high. Then it stopped growing (around 78% usage of 4 GB), and the speed collapsed. So that looked like some caching problem.