Performance Scaling Factor
When you combine multiple units into a cluster, you can expect the total cluster performance to be approximately 80% of the maximum combined throughput.
For example, for TCP throughput, the Firepower 9300 with 3 SM-40 modules can handle approximately 135 Gbps of real world firewall traffic when running alone. For 2 chassis, the maximum combined throughput will be approximately 80% of 270 Gbps (2 chassis x 135 Gbps): 216 Gbps.