Zabbix is a fairly lightweight monitoring application that is able to manage thousands of items with a single-server installation. However, the presence of thousands of monitored hosts, a complex network topology, or the necessity to manage different geographical locations with intermittent, slow, or faulty communications can all show the limits of a single-server configuration. Likewise, the necessity to move beyond a monolithic scenario towards a distributed one is not necessarily a matter of raw performance, and, therefore, it's not just a simple matter of deciding between buying many smaller machines or just one big, powerful one. Many DMZs and network segments with a strict security policy don't allow two-way communication between any hosts on either side, so it is impossible for a Zabbix server to communicate with all the agents on the other side of a firewall. Different branches in the same company or different companies in the same group may need...