how can i set that up?
MfG
Conventional:
One harddrive for nextcloud - web/php directories
One harddrive for the database
One harddrive for the data directory
Logical volumes (serveral different sizes):
Connect them into one volume and use it as one huge drive
RAID (same size):
Connect them as RAID drives (RAID 0,1,5,10,50 - depends) and use them as one huge drive
I remeber there is somewhere a setting in the gui to add external usb drives.
Flixofon,
You will need to make sure that you have the “external storage” application installed in your “NextCloud” installation:
If that is installed and enabled then you will have the “External Storage” option in the administrator menu. Click on the option and you will be able to configure local or attached (AWS S3 etc…) volumes
One word of warning, if you’ve installed the snap version then you will have issues in trying to connect mounted volumes (or any directory) - well I am 
.
Regards,
On Linux, you can use LVM to bundle different hard drives to obtain one large storage.
You can, however, the way on how to do it, is highly dependant on your configuration, what os do you run nextcloud on? Are u using something like nextcloudpi or a docker container…