unix - NGINX Serving large files (mp4), extremely inefficiently -

i running nginx/1.0.15 on centos 6.6 os.

the server has following specs:

intel(r) atom(tm) cpu c2750 @ 2.40ghz (8 cores)
32gb ram
5 x 6000 gb 7200 rpm (raid 10)

the problem

the server has 1gbit/s connection, tops out , bottlenecks after 400-500 mbit/s. service starts decline @ 100 connections.. , speed server drops dramatically (despite having 50% bandwidth still available)

the nginx server strictly serving static .mp4 files. each file typically 400-1200mb (700mb being avg.)

i have tried many many configurations , of them give me same results.

is there blatantly wrong or misguided in configuration?

the configurations

/etc/nginx/nginx.conf

user              nginx; worker_processes  9;  error_log  /var/log/nginx/error.log;   pid        /var/run/nginx.pid;   events {     worker_connections  51200;     use epoll;  }  worker_rlimit_nofile 600000;  http {     include       /etc/nginx/mime.types;     default_type  application/octet-stream;      log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '                   '$status $body_bytes_sent "$http_referer" '                   '"$http_user_agent" "$http_x_forwarded_for"';  #access_log  /var/log/nginx/access.log  main; access_log off;  aio on; sendfile        off; tcp_nopush      off; tcp_nodelay      on;  #keepalive_timeout  0; keepalive_timeout  65;  output_buffers 1 3m; #gzip  on;  include /etc/nginx/conf.d/*.conf;  open_file_cache          max=10000 inactive=5m; open_file_cache_valid    2m; open_file_cache_min_uses 1; open_file_cache_errors   on;  } 

/etc/nginx/conf.d/default.conf

server {     listen       80 default_server sndbuf=32k;     server_name  _;      #charset koi8-r;      #access_log  logs/host.access.log  main;      include /etc/nginx/default.d/*.conf;       location / {         root   /usr/share/nginx/html;         index  index.html index.htm;     }      location /videos/ {         root /home;         gzip off;         gzip_static off;          mp4;         mp4_max_buffer_size   300m;     }      location /stats {         stub_status on;     }      error_page  404              /404.html;     location = /404.html {         root   /usr/share/nginx/html;     }       error_page   500 502 503 504  /50x.html;     location = /50x.html {         root   /usr/share/nginx/html;     } }