1. Things to Note

If you want to backup a VM with a passed through drives then I would recommend to only backup the VM disks and not the drives. For instance if you have two 18 TB drives passed through to a TrueNas VM  then you don't want to back these ones up with PBS. That is because TrueNas has its own backup solution for datasets. To turn off backing up all the disks simply go to the VM

Then Hardware and double click on the drives you don't want to backup with PBS. Then click advanced, and you will see the backup box. Makes sure you untick this box. This will then make sure that the passed thorugh drives are not backed up by PBS since this can take ages especially if the drives are big.