OpenVPN on OpenWRT - where are the speed problems?

Question

openvpn

Good afternoon, colleagues
There are two TPLink WR1043ND routers (CPU 400Mhz, RAM 32MB, Flash 8MB) with OpenWRT Attitude Adjustment 12.09 firmware installed. Flash drives are connected to the routers, on which the system partition has been transferred and a partition for swap has been created.
OpenVPN rises between routers

port 1199
proto udp
dev tun

ca /etc/openvpn/keys/ca.crt
cert /etc/openvpn/keys/GW-2.crt
dh /etc/openvpn/keys/dh1024.pem
key /etc/openvpn/keys/GW-2.key
cipher BF-CBC
auth MD5

server 132.1.1.0 255.255.255.0
route 192.168.11.0 255.255.255.0

ifconfig-pool-persist /etc/openvpn/ipp.txt
client-config-dir /etc/openvpn/ccd

keepalive 10 120
comp-lzo yes
max-clients 10
persist-key
status openvpn-status.log
log /var/log/openvpn.log
verb 9

So the speed between routers
without a tunnel is ~ 1000KB / s
in the tunnel ~ 200KB / s
Therefore, I have three questions:
1 Is such a speed drop in the tunnel 4-5 times normal? What speed can you really get?
2 What can be changed in OpenVPN settings to improve speed
3 Despite the fact that it seems to me that these routers are quite good and the task is not so difficult (there is no other load on routers. Each has a network for 4 machines: DHCP, DNS , NAT and all ..), but if someone has a ready-made recipe for an OpenVPN channel on equipment of a similar price range, I'm ready to change routers to a pair of DLink, ASUS, or, for example, Mikrotik (although I've never dealt with them) .
PS The next thing I plan to do (it will not turn out before the weekend)
1 - I'll try to abandon the swap on a flash drive and the system on a flash drive. Maybe flash drives are slow.
2 - I'll try to use a static key for OpenVPN instead of certificates.

Answer 1

Have you looked at the load on the routers? Maybe there is not enough processor power?

Answer 2

Try disabling compression comp-lzo no
Also check mtu

Answer 3

In general, the load of the router acting as an OpenVPN server really reached 100%. Played with compression - nothing has changed. So far, disabling logging has helped the most - the download at the peak has dropped to 95% and the speed has increased to 16.7Mb / s.
I would also like to reduce the load on the processor - I'll play around with the key length. By the way, the client is also loaded up to 80%