Top 5 Best System Monitoring Tools (02.11.2009)
Why is OMD the Best Open Source Monitoring Solution over Zabbix, Zenoss or Sensu (28.11.2013)

• Use Nagios to check Services (Aapche, Servers, Network, Qmail, MySQL, MemCached, Disk Space, Memory etc) Availability and Manage Alerts.
• Use Cacti to make Services (Apache, MySQL, MemCached, Redis, etc) performance graphs.

What is the difference between nagios xi and cacti for monitoring?

The main components of OMD are Check_MK, PNP4Nagios, Nagvis, and of course Nagios.

• OMD – The Open Monitoring Distribution
• The Check_MK Monitoring System
• PNP4Nagios
• NagVis
• Nagios – The Industry Standard In IT Infrastructure Monitoring