Maxtor... First check your nginx error log file and php error log. Set worker_processes to the number of cores your system has. If you've 2 core set it to 2. The max number of open files (File Descriptors) resource limit for nginx need to be configured to avoid error 500.
`And Make sure space is left on file system (df -h).
`Make sure space is left on /tmp file system and most important /tmp permission must be set to 1777 (ls -ld /tmp and ls /tmp)
`Can you post the error message from your logs (tail -f /var/log/nginx/nginx_error.log and tail -f /var/log/nginx/php_fastcgi_error.log)?
`Can you post the filedescriptors limits?(su - nginx && ulimit -Hn && ulimit -Sn)? then i can help more..
Adjust path, username and dirs as per your setup.
@raj, noop, Internet connection speed will never (in rare case it is possible; e.g., reverse proxy and ddos) results into error 500; this is server side error and need to be fixed at os and nginx level only.
`Thanks....