Abysmally slow write to geom class volume over network

[Michael Osipov]

Hi folks,

I am experiecing a performance breakdown when writing to some geom class 
volume over network. I have tried SCP/SFTP, SMB, nc, ggated/ggatec from 
Windows 10 and FreeBSD 10.3-RELEASE and I receive at most 500 kB/s. 
Reading is superfast as well as writing to a regular, non-geom volume, 
network is fully saturated.

I am on:
# uname -a
FreeBSD bsd1home 10.3-RELEASE-p7 FreeBSD 10.3-RELEASE-p7 #0: Thu Aug 11 
18:37:29 UTC 2016 
root at amd64-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC  i386

Any idea what the problem is? How can I investigate on the penality in 
performance?

Thanks,

Michael