How to find out what the server is loading?

Question

Nginx

Periodically, the server starts to use all 100% of the capacity. It lasts from several minutes to an hour.
Used 100 ram and cpu. The disk starts reading at a maximum of 300 kb / s. The problem is that when such an attack occurs, you will not connect to the server even via ssh. It helps only reboot from the hosting panel or just wait until it passes by itself.
There are two dozen sites on the server, it is painfully long to study the logs. From what side to approach the solution of the problem?

Answer 1

You can try atop .
Well, in general, some kind of monitoring (Munin, Zabbix, etc) can fix a similar problem.

Answer 2

Install monitoring on the server, more precisely - the monitoring agent on the server, and where it will send data - to another. Then the maximum data will be removed right by the time the brakes start. And even during them, the agent will have time to receive processor time and send data.

Answer 3

what about the htop command?