Diagnosis

• DNS
• Network Diagnosis
• PHP Errors
• Slow Website
• SSH Diagnosis

If a server is having issues and you can still access it through one or more services (SSH, MySQL, HTTPD, etc.), then check these areas:

• monit: What is the system load? What is the memory usage?
• collectd: Are there any trends of increasing loads or memory usage?
• System, Apache, MySQL logs: check for anomalies

If you can't access a server through any services, then run these tests:

• Check DNS records to see if they are resolving correctly
• Log into web hosting control panel to see status

• pidstat