nginx and VirtualBox, heavy load

[John Moore]

I have been using nginx very successfully as a reverse proxy (in front 
of a bank of web servers) on Linux. For a special project I'm working 
on, we were hoping to use the same setup but running in a Linux virtual 
machine under VirtualBox, hosted on a Windows 2003 Server machine 
(forced on us by other software considerations!). I've been a little 
disappointed in my stress testing (with ab and my own Java testing tool) 
to find that under heavy load (multiple concurrent users), a lot of 
requests are failing, with the error being the 'connection reset by 
peer'. Now, I'm not sure that the requests are even reaching nginx (is 
there a way to tell?), but if it is, what might be causing this error? 
And if this is in fact OT and it's a networking problem, can anyone give 
me any pointers :)? I should say that this using VirtualBox's NAT and 
in-built port forwarding. nginx is 0.6.35, on Ubuntu.

Incidentally, I should say that the testing I've been doing is designed 
to be pretty harsh, and for less heavily loaded sites or sites where the 
occasional dropped request isn't critical, the VirtualBox solution is 
great and I'm very impressed with how good the performance is. (I use VB 
in my daily work life to run an Ubuntu VM on my Windows Vista laptop. 
Ugh, I just said the V word, I'm going to have to go and wash my mouth out).