Heavy internal network traffic seems to upset other network processes

[Jim Keller]

I have a FreeBSD 6.1 machine with two em nics, one of which is set up as 
external for the Internet-facing side, the other is internal (100Mbit) 
and is connected to a small switch with a few other machines. 
Occasionally I will transfer large files across the internal link and, 
when doing so, other network related applications seem to grind to a 
halt and the system seems to be working very hard. In fact, mySQL will 
actually stop accepting incoming requests during the file transfer, 
which is the biggest side effect I'm having because of the problem. I'm 
wondering if it's some kind of tuning option I need to set, but I'm 
really not sure where to look. I have maxusers set to 256, nmbclusters 
is 8192 (maybe this should be higher?). Any help would be appreciated. 
Thanks.

-Jim keller