Gluster users - Oct 2017 - bonding mode

I'm testing GlusterFS and Lizard.
I've set both SDS in replica 3.

All servers are configured with bonding mode "balance-rr" with 2x1Gbps
nic
With iperf i'm able to saturate both link with a single connection.
With Lizard i'm able to saturate both link with a single "dd"
write

With gluster i'm able to saturate only one link, reaching about 35MB/s
(35*3*8 = 840mbit/s = 1 link only)

Any clue why gluster isn't able to use both links ?