Bandwidth LACP bonding

Hi everyone, I'm doing bandwidth tests between my PC with centos 7 and my SAN. I created a bonding mode=4 on the server of three 10 Gb network interfaces and set the LACP on three 10 Gb network ports in the SAN. All three ports of the server and SAN are connected to a management switch where the LACP is configured. I connect 3 ISCSI volumes to the server and do some bandwidth tests trying to saturate the network but I see that only a 10 Gb network card is being used. I start two copy processes that write to two different volumes and I always only use a 10Gb network card. I change the xmit_hash_policy value and set it to layer3+4 but nothing changes. Since the SAN has dual controllers, I configure and create two more ISCSI volumes on the second controller and mount them on the server. I test the copy from the server by starting two copy processes. One writes on controller 1 and one on controller 2. In this way I see that both network cards are used at maximum performance (10 Gb for each network card are saturated) I start 4 copy processes to also saturate the third network card but it is not used. I don't understand how to use all the network cards configured in LACP on the server. I don't really understand how LACP works. When does it use all network ports? Are there parameters on the server that I need to set to make it use all network cards? Thanks in advance.