[Samba] Samba 4 fileserver perfomance

[Александр Свиридов]

I have at home two centos boxes:
Box A - centos 6.4. gui version
Box B - centos 7.1. minimal version.
They are connected to 100Mb router (both boxes have 100Mb network adapters). Box B has software raid 1 and sata II interfaces. On box B samba4 is installed and I copy files to samba share ( from box A to box B). 

Network monitor (iptraf-ng) shows only 20000 kbps of this copying operation. That is around 2MB per second. CPU load on box B is around 20% on CPU1 and 1-2% on CPU2.
I've checked the network speed between A (server) and B(client) via iperv:
[root at localhost P]# iperf -c a.a.a.a
------------------------------------------------------------
Client connecting to a.a.a.a, TCP port 5001
TCP window size: 22.5 KByte (default)
------------------------------------------------------------
[  3] local b.b.b.b port 53459 connected with a.a.a.a port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec   112 MBytes  94.3 Mbits/sec

So I think that only samba 4 can be problem in this configuration. How to increase samba 4 fileserver perfomance?
 In internet people say to modify socket options but https://wiki.samba.org/index.php/Performance_Tuning says no to do it?

How to solve problem of such poor perfomance?