I'm running a Nginx powered server I have configured a while ago. One problem I have on my Drupal sites hosted on that environment is that I couldn't upload a files larger than 1MB using Drupal fields. I got Nginx: 413 Request Entity Too Large error.
And it pissed me of - because of - in my php.ini file I had already set a maximum upload file size to some 192MB.
When I faced a situation, when I had to upload files larger than 1MB, I went on my searches, what's wrong with my server, after 1 minute search I found a solution here:
http://www.cyberciti.biz/faq/linux-unix-bsd-nginx-413-request-entity-too-large/
sudo nano /usr/local/nginx/conf/nginx.conf
add the following line to http section
# set client body size to 2M # client_max_body_size 2M;
save and exit
Restart the Nginx server
sudo /etc/init.d/nginx stop
sudo /etc/init.d/nginx start