Zabbix provides flexible functionality over Nagios and other open source monitoring softwares like opennms, zenoss etc. It is widely used in market these days due to its easy administration and configuration.
Pros:- 1. Zabbix provides a user friendly GUI interface for administration and configuration for monitoring servers and network.
2. Zabbix is open source software, so no licenses needs to be purchased.
3. Zabbix clients can be configued easily by installing Zabbix client software on client machines on the network. Zabbix client machines can be of either windows, linux or any unix machine.
4. User parameters can be configured for customized scripts.
5. Configuration/administration documentations are available on official web site of Zabbix and videos/additional documentations are also available on other popular websites like youtube etc.
Cons:- 1. Installation is little complex, tedious, time consuming and prone to user errors. However, once installed, it provides user friendly interface for all administrative tasks.
2. Some scripting knowledge is required in order to make changes to configuration files.
3. Adding custom services requires reloading the config or restarting the service.
Alternate Vendors:- Nagios, Zenoss, Cacti !!