In a traditional fleet configuration, the capacity in the fleet comprises a base-line of bare metal machines that are always available, and integrations with cloud providers that allow the fleet to burst into the cloud when the number of concurrent players exceeds the bare metal machine capacity.
The line in the preceding graph indicates the number of allocated game servers. When the solid line lowers below the dashed line, there is no need for capacity above the base-line of bare metal machines. When the solid line rises above the dashed line, there is more demand for game servers than the base-line that bare metal can support, so the reactive scaler bursts into the cloud. Because the game servers running on the bare metal machines are static, the total number of game servers within a fleet doesn't lower below the number of game servers hosted on bare metal (the dashed line represents this in the graph). Therefore, the total number of servers is independent from the number of allocated servers.
An optional (but highly recommended) feature of the reactive scalers exists to keep a buffer of available servers, which keeps a gap between the total number of servers and the number of allocated servers. This enables players to quickly join a game session.
