NMRiH srcds - Server lagging when there are over 70 zombies

[xxtoxiic]

Hey, I got my own No more room in hell server with 2 cpu cores (i7) 2 x3.30ghz , 1GBit Connection, 2 GB Ram (I think, it should be enough for srcds)

Now my problem.

If there are over 70 zombies, the server laggs (my ping goes from 60 -> 120-150).

Ram is only 350mb used, CPU is 5-10% used.

Anyone know wheres the problem?

Thanks in advance.