It's a good feeling to have a backup when things go wrong. When setting up a monitoring system, it's a good idea to spend some time to figure out how backups could be made so that the good feeling isn't replaced by a bad feeling. With Zabbix, there're components and data to be considered:

• Zabbix binaries: Such as the binaries from Zabbix server, proxy, and agent. They're probably not worth backing up. Hopefully, they're easily available from packages or by recompiling.
• Zabbix frontend files: Hopefully, they're easily available as well. If any changes have been made, they're presumably stored as a patch in a version control system.
• Zabbix configuration files: Hopefully, these are stored in a version control system or a system configuration tool.
• Zabbix server database: This contains all of the monitoring-related configuration data, such as hosts and items, and it holds all of the collected values. Now that's worth backing up!