the default size for jumbo frames is 9000. So you send 1/6th the number of packets, less headers and tail relative to the amount of data being sent. The real saving is the time it takes to get on the cable, as you’re transmitting a 1/6 of the number of frames for the same data, you save on the time to transmit. you also do 1/6th the number of mac checks, so it lowers CPU usage, unless you have a TCPIP off load card.
Always enable it with iSCSI, but check the “path” all support jumbo frames.
Hope it helps