If the server is loading slowly check the below stats in the server

$uptime

12:03:11 up 1 day, 23:23, 2 users, load average: 44.67, 37.02, 30.92

$free -m

it will check for the memory (RAM) available.

$nice top -cd3

It will show details regarding the process consumption.

$mysqladmin proc stat

It will check the mysql process stats

This will show the stats regarding the slow queries.

$attackers 80

It will check for the highest http connection at the port 80

Note : Ip with more than 50 connections to the httpd should be blocked.