maG66

Install the plugin and check the Status URL Link. You can submit it to observo-monitoring.com to monitor it 24/7. 
– shell_exec must be available for cpu and memory 
– The plugin will install an open rest api 
– External servers can access this api to get performance stats 
– Services like observo-monitoring.com can give you an added value
<h3>Credits</h3>
<a href="https://www.observo-monitoring.com" title="Observo Monitoring" rel="nofollow ugc">Observo Monitoring</a>

Observo Monitoring

Monitor your Server Memory, Disk and CPU from external server

Bastien Ho

NOUS Open Usefull &amp; Simple

Not tested on non linux hosted sites !
WordPress monitoring, displays for the super admin, the server ressources on the (network) dashboard
<ul>
<li>hostname and distro</li>
<li>size of the wp-content directory</li>
<li>available memory</li>
<li>space used on linux partitions</li>
<li>process running on the servers</li>
</ul>

Ressources

Monitoring the server resources with dashboard widgets

Observo Monitoring vs Ressources