Is it possible that this is DDoS and how to deal with it?

Question

linux

Hey!
The project worked intermittently on server A , transferred the domain to server B and at the same moment all pages began to lag very badly. They load ~ 5-9 seconds, despite the fact that the CPU load is 3%, and there are no more than 20 people on the site.
What does it mean?
Both servers have 16 GB of RAM Nginx latest stable.

Answer 1

Hello, my diagnosis is wrong.

Answer 2

look at the logs and top
and it will immediately become clear

Answer 3

iotop -oka
to STUDIO