high Traffic setup problem, module status don't deliver data

[Aleksandar Lazic]

Dear list member.

currently we have a huge traffic come up.

~500 r/s
http://download.none.at/nginx_request-day.png

~3.5K active connections
http://download.none.at/port_www-day.png
http://download.none.at/nginx_combined.png

The Peaks are the raw values from module status.

~1.1g b/s traffic
http://download.none.at/if_eth2-day.png
http://download.none.at/tcp-day.png

I have tried to setup the machine for this traffic but it looks to me 
that was not successfully.

HW:
24 CPUs
Memory: 49381124k/52166656k available (7176k kernel code, 1897452k 
absent, 888080k reserved, 6067k data, 1016k init)

OS:
lsb_release -a
No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu 12.04.4 LTS
Release:	12.04
Codename:	precise

Nginx:
/home/nginx/server/sbin/nginx -V
nginx version: nginx/1.4.4
built by gcc 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5)
TLS SNI support enabled
configure arguments: --prefix=/home/nginx/server --with-debug 
--without-http_uwsgi_module --without-http_scgi_module 
--without-http_empty_gif_module --with-http_stub_status_module 
--with-http_gzip_static_module --with-http_ssl_module --user=nginx 
--group=www-data --with-file-aio --without-http_ssi_module 
--with-http_secure_link_module --with-http_sub_module 
--with-http_spdy_module

Conf:
http://download.none.at/my_nginx.conf

When I activate the aio, nginx and xfs crashes, that's why aio is not 
active.

In one include file we have the following.

####
         location ~ recent {
           add_header Cache-Control "no-cache";
         }
####

sysctl -a
http://download.none.at/sysctl.txt

lsmod:
http://download.none.at/lsmod.txt

dmesg:
http://download.none.at/dmesg.txt

On this machine also runs a postgresql and php-fpm but the current 
traffic is from delivering of pictures from the file system.

/dev/mapper/pada2_vg-pada2_lv on /home/<datadir> type xfs 
(rw,noatime,nodiratime,attr2,inode64,noquota)

Thanks for help.

Best regards
Aleks