I just successfully installed NethServer on OVH, but there are some problems accessing centos-base and centos-updates from NethServer.repo.
OVH machines resolve host names with IPv6 and CentOS mirror report different answers if queried with IPv4 or IPv6.
To install NethServer on OVH:
yum localinstall -y http://mirror.nethserver.org/nethserver/nethserver-release-6.6.rpm
rpm --import /etc/pki/rpm-gpg/*
yum --disablerepo=* --enablerepo=nethserver-base,nethserver-updates,base,updates install @nethserver-iso
/sbin/e-smith/signal-event system-init
eorepo nethserver-base nethserver-updates base updates
Also, at the end of the system-init event the machine was stuck and required a reboot.
At the end, I would suggest Digital Ocean over OVS at least for NethServer installations.
Thanks to @enrilor for the collaboration
P.S. If someone needs more technical details about the problem, please feel free to ask.