if it only were so easy...
I did some tests with an S150 class SSA a while back, using 1G ports at 100Mbps. Without any QoS configuration, sending 110Mbps data to one 100Mbps port resulted in a steady buffer use of about 4MiB (after ramp-up to fill the buffer) before dropping packets, inducing about 340ms of latency. The 1G port is documented in the FAQ as having 21.3MB of packet buffer, so obviously not all of that was used. I used two input ports to one output port for the tests.
I did not find any way to configure how much packet buffer to use on the S-Series. For EXOS, there is a way to display and configure packet buffer sizes, see How to change port buffer size