TF2 server periodic lag spikes

[nnnta]

BASIC INFO
Server OS: Ubuntu Server 12.04 LTS 64-bit
Processor: Phenom II X6 1055T
Ram: 4x4 GB
Game(s): TF2 x 6 (tied via cpu affintiy to 1 per core, 16 to 24 players each)
Start Up Command: Using this script for all 6 instances. http://forums.srcds.com/viewtopic/5835
Admin Mods: SourceMod, MetaMod

NETWORK AND BANDWIDTH INFO
Bandwidth: 100mbps down 50mbps up
Router: PfSense 2.0.1-RELEASE (i386) on E4500 6GB ram with dual intel nic's
Local IP of Server: 192.168.10.101
External IP: bakemono.servegame.org
Port Forwarding Screen Shot: http://i.imgur.com/4IYYj.png

Servers run smooth most of the time until the random freeze spikes hit it. It affects all players (including me playing via LAN) in the server instance (not sure if it occurs in all server instances). When the freeze spike hits, the players connection to the server flatlines for around 3 to 5 seconds before resuming normality. So this is likely to be a configuration or hardware issue with the server itself.

The server was running windows server 2008 R2 prior to this and had similar problems.

Things I'm going to try:
optimize linux kernel http://wiki.fragaholics.de/index.php/EN:Linux_Kernel_Optimization
optimize ext4 filesystem
optimize network stack settings

[nnnta]

anyone?

[scso1502]

This is likely a network connection issue. I recommend downloading Pingblotter Standard (free download at: http://www.pingplotter.com/) and monitor your network while you play. If you see a spike on the monitor that coincides with your freeze, you've got your answer.

[Doggie52]

Are you hosting this on your own network? Then I definitely concur with scso, try monitoring your network connectivity and see if you can narrow it down to your connection. It doesn't sound at all like a hardware issue, you wouldn't have those kind of symptoms. I doubt it's a configuration issue since "The server was running windows server 2008 R2 prior to this and had similar problems."

[PAL-18]

Do you have hyperthreading enabled? If so, there's your problem. I used to have it enabled and all my servers suffered from this problem. After disabling it, the problem went away.

I asked Valve about it and they said that the server is not multi-threaded and can't make use of virtual cores (which is what hyperthreading is).