No problem, my first information was a bit rare I think.
Maybe I'll start setting up the two OMV systems without LUKS and change that later when the plugin is ported to OMV6
This would mean I have to delete the existing file system, setup LUKS and then creating a new file system on top of LUKS and copy my data back from the backup, right? Or are there any drawbacks of that approach?
Assuming [...] you don't have a backup of all your data.
Maybe I have to explain my setup a bit more in detail: Actually, I will set up two OMV systems, one at location A and one at location B. The hardware I've mentioned above is the one of A, the hardware of B is older, but in principle the same configuration. B is running with Windows Server Essentials since several years, but I want to get rid of it.
My backup concept (because I know RAID isn't one) will be realized over two ways (at least that's what I imagine):
a) The two OMV systems shall always have same version of data. This is also because I sometimes work at location A, sometimes at location B and always want to have maximum speed over LAN.
b) A 'true' backup for those cases you've mentioned above (virus, accidentially deleting files etc.)
Using the second internal drive for backup instead of RAID will not protect me against viruses encrypting my data, because it's always connected. In my opinion, the only option is an external drive physically not connected combined with my own attention realizing the attack before connecting the external drive next time.
The encryption is just in case of a theft of the complete NAS or an external drive.
As a consequence of all the above, I would install OMV on a 32GB pendrive and dedicate the SSD to docker.
That's a good point, I will think about that.
To install openmediavault-luksencryption you need to install omv-extras.
OMV-Extras.org Plugin
Then go to System> Plugins> Search for the plugin and click install.
You can see here the progress of the plugins in OMV6
omv-extras plugins - porting progress to OMV 6.x
omv-extras is already installed, but I didn't find the openmediavault-luksencryption plugin last time.
But as I can see at the page with the porting progress you've linked, it's not yet ported to OMV6 
Seems I have to be patient... or is there another way get LUKS running without destroying complete OMV system?
Hello,
I'm new here in the forum and hope to find some answers to my questions. 
Currently I'm setting up my NAS which looks as follows:
My plans look very similar to atreo ones:
Is it possible to run the luksencryption-Plugin at OMV6? If yes, how can I install it?
