Site crashes while cpu usage is not high

[steeve88]

Hi all,

I have developed a site on a centos7:
if I run that: rpm --query centos-release
I get that: centos-release-7-4.1708.el7.centos.x86_64

The server is i7, 64GB. I have some weather cameras, which update every 10''. I 've recently moved to this much powerful server. Previously, my site was on a shared server. However, even if the overall cpu usage is only 5-20% (sometimes up to 40%), the site lags and sometimes doesn't load. I also checjed the number of visitors and I can say that on the previous server the site was fine with these statistics in general.
What should I do for that? Any ideas?

Thank you in advance