Banana Pi overclocking and MTU setting

hi,

since 2 days i am using on my Banana Pi the Debian Jessie with 4.8.15 Kernel with installed Openmediavault 3.

The system is working stable, but the network-performance is less then my older Installation based on Debian Wheezy with Openmediavault 2.

I tried change the MTU-Size to 9000 and overcklocking up to 1.2 GHz, booth is not possible.

I don´t know why ?

For the setting the MTU-Size i edited /etc/network/interfaces and added the value "mtu 9000" -> no effects

I tried set the MTU over the OMV WebGUI under network settings -> no effects.

ifconfig shows me MTU=1500

Booth ways was at Debian Wheezy possible.

At Debian Wheezy i had overclock the CPU up to 1.2 Ghz. The system was stable 1 year.

For this i edited the files from cpufrequtils (/sys/device/system...........)

At the new system i can edit the values, but after them the values will be reset to standard values.

I found many many manuals in the internet, but is´nt working.

Can you help me? Step by step.......... ;-)

I´m sorry for my englisch, i´m from poland, in the school i had to learn russian ................. :-((((